Air filtration arrangements having fluted media construction and methods

ABSTRACT

Filter arrangements include a barrier media in the form of fluted media treated with a deposit of fine fibers. The media is particularly advantageous in high temperature (greater than 140 to 240° F.) systems. Such systems may include engine systems, gas turbine systems, and fuel cell systems. Filter arrangements may take the form of media packs having a circular cross-section or a racetrack shaped cross-section, or media packs formed in a panel configuration.

This application is a continuation of application Ser. No. 10/741,788,filed Dec. 19, 2003, now U.S. Pat. No. 6,974,490, which application is acontinuation of application Ser. No. 09/871,590, filed May 31, 2001, nowU.S. Pat. No. 6,673,136, which application claims priority under 35U.S.C. § 119(e) to U.S provisional application Ser. No. 60/230,138,filed on Sep. 5, 2000, which applications are incorporated by referenceherein.

FIELD OF THE INVENTION

The invention relates to a filter arrangement and filtration method.More specifically, it concerns an arrangement for filtering particulatematerial from a gas flow stream, for example, an air stream. Theinvention also concerns a method for achieving the desirable removal ofparticulate material from such a gas flow stream.

The present invention is an on-going development of Donaldson CompanyInc., of Minneapolis, Minn., the assignee of the present invention. Thedisclosure concerns continuing technology development related, in part,to the subjects characterized in U.S. patents: U.S. Pat. No. B24,720,292; Des 416,308; U.S. Pat. Nos. 5,613,992; 4,020,783; and5,112,372. Each of the patents identified in the previous sentence isalso owned by Donaldson, Inc., of Minneapolis, Minn.; and, the completedisclosure of each is incorporated herein by reference.

The invention also relates to filters comprising a substrate having afine fiber layer made of polymer materials that can be manufactured withimproved environmental stability to heat, humidity, reactive materialsand mechanical stress. Such materials can be used in the formation offine fibers such as microfibers and nanofiber materials with improvedstability and strength. As the size of fiber is reduced thesurvivability of the materials is increasingly more of a problem. Suchfine fibers are useful in a variety of applications. In one application,filter structures can be prepared using this fine fiber technology. Theinvention relates to polymers, polymeric composition, fiber, filters,filter constructions, and methods of filtering. Applications of theinvention particularly concern filtering of particles from fluidstreams, for example from air streams and liquid (e.g. non-aqueous andaqueous) streams. The techniques described concern structures having oneor more layers of fine fibers in the filter media. The compositions andfiber sizes are selected for a combination of properties andsurvivability.

BACKGROUND OF THE INVENTION

Gas streams often carry particulate material therein. In many instances,it is desirable to remove some or all of the particulate material from agas flow stream. For example, air intake streams to engines formotorized vehicles or power generation equipment, gas streams directedto gas turbines, and air streams to various combustion furnaces, ofteninclude particulate material therein. The particulate material, shouldit reach the internal workings of the various mechanisms involved, cancause substantial damage thereto. Removal of the particulate materialfrom the gas flow upstream of the engine, turbine, furnace or otherequipment involved is often needed.

The invention relates to polymeric compositions with improved propertiesthat can be used in a variety of applications including the formation offibers, microfibers, nanofibers, fiber webs, fibrous mats, permeablestructures such as membranes, coatings or films. The polymeric materialsof the invention are compositions that have physical properties thatpermit the polymeric material, in a variety of physical shapes or forms,to have resistance to the degradative effects of humidity, heat, airflow, chemicals and mechanical stress or impact.

In making fine fiber filter media, a variety of materials have been usedincluding fiberglass, metal, ceramics and a range of polymericcompositions. A variety of fiber forming methods or techniques have beenused for the manufacture of small diameter micro- and nanofibers. Onemethod involves passing the material through a fine capillary or openingeither as a melted material or in a solution that is subsequentlyevaporated. Fibers can also be formed by using “spinnerets” typical forthe manufacture of synthetic fiber such as nylon. Electrostatic spinningis also known. Such techniques involve the use of a hypodermic needle,nozzle, capillary or movable emitter. These structures provide liquidsolutions of the polymer that are then attracted to a collection zone bya high voltage electrostatic field. As the materials are pulled from theemitter and accelerate through the electrostatic zone, the fiber becomesvery thin and can be formed in a fiber structure by solvent evaporation.

As more demanding applications are envisioned for filtration media,significantly improved materials are required to withstand the rigors ofhigh temperature 100° F. to 250° F., often 140° F. to 240° F. and up to300° F., high humidity 10% to 90% up to 100% RH, high flow rates of bothgas and liquid, and filtering micron and submicron particulates (rangingfrom about 0.01 to over 10 microns) and removing both abrasive andnon-abrasive and reactive and non-reactive particulate from the fluidstream.

Accordingly, a substantial need exists for polymeric materials, micro-and nanofiber materials and filter structures that provide improvedproperties for filtering streams with higher temperatures, higherhumidities, high flow rates and said micron and submicron particulatematerials.

A variety of air filter or gas filter arrangements have been developedfor particulate removal. However, in general, continued improvements aresought.

SUMMARY OF THE INVENTION

Herein, general techniques for the design and application of air cleanerarrangements are provided. The techniques include preferred filterelement design, as well as the preferred methods of application andfiltering.

In general, the preferred applications concern utilization, within anair filter, of Z-shaped media, including a composite of a substrate andfine fibers, to advantage.

The filter media includes at least a micro- or nanofiber web layer incombination with a substrate material in a mechanically stable filterstructure. These layers together provide excellent filtering, highparticle capture, and efficiency at minimum flow restriction when afluid such as a gas or liquid passes through the filter media. Thesubstrate can be positioned in the fluid stream upstream, downstream orin an internal layer. The fiber can be positioned on the upstream, thedown stream or both sides of a filter substrate, regardless of filtergeometry. The fiber is generally placed on the upstream side. However iscertain applications downstream placement can be useful. In certainapplications, double sided structure is useful. A variety of industrieshave directed substantial attention in recent years to the use offiltration media for filtration, i.e. the removal of unwanted particlesfrom a fluid such as gas or liquid. The common filtration processremoves particulate from fluids including an air stream or other gaseousstream or from a liquid stream such as a hydraulic fluid, lubricant oil,fuel, water stream or other fluids. Such filtration processes requirethe mechanical strength, chemical and physical stability of themicrofiber and the substrate materials. The filter media can be exposedto a broad range of temperature conditions, humidity, mechanicalvibration and shock and both reactive and non-reactive, abrasive ornon-abrasive particulates entrained in the fluid flow. When in normaloperation, the filter is generally exposed to air at or near ambientconditions or at slightly elevated temperature. The filter can beexposed to higher temperature when the engine is operated abnormally orwhen the engine is shut down after extended service. If the engine isnot in operation, air does not pass through the filter. The filterrapidly reaches under hood temperature. Further, the filtration mediaoften require the self-cleaning ability of exposing the filter media toa reverse pressure pulse (a short reversal of fluid flow to removesurface coating of particulate) or other cleaning mechanism that canremove entrained particulate from the surface of the filter media. Suchreverse cleaning can result in substantially improved (i.e.) reducedpressure drop after the pulse cleaning. Particle capture efficiencytypically is not improved after pulse cleaning, however pulse cleaningwill reduce pressure drop, saving energy for filtration operation. Suchfilters can be removed for service and cleaned in aqueous or non-aqueouscleaning compositions. Such media are often manufactured by spinningfine fiber and then forming an interlocking web of microfiber on aporous substrate. In the spinning process the fiber can form physicalbonds between fibers to interlock the fiber mat into a integrated layer.Such a material can then be fabricated into the desired filter formatsuch as cartridges, flat disks, canisters, panels, bags and pouches.Within such structures, the media can be substantially pleated, rolledor otherwise positioned on support structures.

The filter arrangements described herein can be utilized in a widevariety of applications including, for example, dust collection, aircompressors, on-road and off-road engines, gas turbine systems, powergenerators such as fuel cells and others.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a typical electrostatic emitter driven apparatus forproduction of the fine fibers of the invention.

FIG. 2 shows the apparatus used to introduce fine fiber onto filtersubstrate into the fine fiber forming technology shown in FIG. 1.

FIG. 3 is a depiction of the typical internal structure of a supportmaterial and a separate depiction of the fine fiber material of theinvention compared to small, i.e. 2 and 5 micron particulate materials.

FIGS. 4 through 11 are analytical ESCA spectra relating to Example 13.

FIG. 12 shows the stability of the 0.23 and 0.45 microfiber material ofthe invention from Example 5.

FIGS. 13 through 16 show the improved temperature and humidity stabilityof the materials of Examples 5 and 6 when compared to unmodified nyloncopolymer solvent soluble polyamide.

FIGS. 17 through 20 demonstrate that the blend of two copolymers, anylon homopolymer and a nylon copolymer, once heat treated and combinedwith additives form a single component material that does not displaydistinguishable characteristics of two separate polymer materials, butappears to be a crosslinked or otherwise chemically joined single phase.

FIG. 21 is a schematic view of an engine system in which air cleanersaccording to the present disclose may be utilized;

FIG. 22 is a schematic, perspective view of one embodiment of a filterelement that may be utilized in the system depicted in FIG. 21;

FIG. 23 is a schematic, perspective view of a portion of filter media(Z-media) useable in the arrangement of FIG. 22;

FIG. 24 is a schematic, cross-sectional view of the filter elementdepicted in FIG. 22 installed within a housing;

FIG. 25 is a fragmented, enlarged, schematic view of one embodiment of acompressible seal member utilized in a sealing system for the filterelement of FIG. 22;

FIG. 26 is a schematic, perspective view of another embodiment of afilter element that may be utilized in the engine system of FIG. 21;

FIG. 27 is a schematic, cross-sectional view of the filter element ofFIG. 26 installed within a housing;

FIG. 28 is a schematic, exploded, perspective view of another embodimentof a filter element and housing that may be utilized in the enginesystem of FIG. 21;

FIG. 29 is a schematic depiction of a gas turbine system in which filterelements according to the present disclosure may be utilized;

FIG. 30 is a schematic, perspective view of one embodiment of a filterelement that may be useable in gas turbine air intake systems depictedin FIG. 29;

FIG. 31 is a rear elevational view of the filter element depicted inFIG. 30 installed within a tube sheet, and having a prefilter installedupstream of the filter element of FIG. 30;

FIG. 32 is an enlarged, schematic, fragmented, cross-sectional view ofthe air filter arrangement of FIG. 31, taken along the line 12—12 ofFIG. 31;

FIG. 33 is a schematic view of an air intake system for a microturbinesystem, in which filter elements of the present disclosure may beutilized;

FIG. 34 is a schematic, cross-sectional view of a filter element in anoperable installation to clean intake air in a gas turbine system, thecross-section being taken along the line 14—14 of FIG. 35, but in anassembled state;

FIG. 35 is an exploded, side elevational view of the filter arrangementof FIG. 34, and in an unassembled state;

FIG. 36 is a fragmented, schematic, cross-sectional view showing thefilter element sealed within a filter housing;

FIG. 37 is a schematic view of an air intake for a fuel cell system,which may utilize filter elements disclosed herein;

FIG. 38 is a schematic, cross-sectional view of a filter assembly thatmay be utilized in the fuel cell air intake system of FIG. 37; and

FIG. 39 is a schematic, cross-sectional view of another embodiment of afilter assembly that may be utilized in the air intake for a fuel cellsystem.

DETAILED DESCRIPTION OF THE INVENTION A. Micro Fiber or Fine FiberPolymer Materials

The invention provides an improved polymeric material. This polymer hasimproved physical and chemical stability. The polymer fine fiber(microfiber and nanofiber) can be fashioned into useful product formats.The fiber can have a diameter of about 0.001 to 10 microns, about 0.005to 5 microns, about 0.01 to 0.5 micron. Nanofiber is a fiber withdiameter less than 200 nanometer or 0.2 micron. Microfiber is a fiberwith diameter larger than 0.2 micron, but not larger than 10 microns.

This fine fiber can be made in the form of an improved multi-layermicrofiltration media structure. The fine fiber layers of the inventioncomprise a random distribution of fine fibers which can be bonded toform an interlocking net. Filtration performance is obtained largely asa result of the fine fiber barrier to the passage of particulate.Structural properties of stiffness, strength, pleatability are providedby the substrate to which the fine fiber adhered. The fine fiberinterlocking networks have as important characteristics, fine fibers inthe form of microfibers or nanofibers and relatively small spacesbetween the fibers. Such interfiber spaces in the layer typically range,between fibers, of about 0.01 to about 25 microns or often about 0.1 toabout 10 microns. The filter products comprise a fine fiber layer on achoice of appropriate substrate such as a synthetic layer, a naturallayer or a mixed natural/synthetic substrate. The fine fiber adds lessthan 5 microns, often less than 3 microns of thickness. The fine fiberin certain applications adds about 1 to 10 or 1 to 5 fine fiberdiameters in thickness to the overall fine fiber plus substrate filtermedia. In service, the filters can stop incident particulate frompassing to the substrate or through the fine fiber layer and can attainsubstantial surface loadings of trapped particles. The particlescomprising dust or other incident particulates rapidly form a dust cakeon the fine fiber surface and maintains high initial and overallefficiency of particulate removal. Even with relatively finecontaminants having a particle size of about 0.01 to about 1 micron, thefilter media comprising the fine fiber has a very high dust capacity.

The polymer materials as disclosed herein have substantially improvedresistance to the undesirable effects of heat, humidity, high flowrates, reverse pulse cleaning, operational abrasion, submicronparticulates, cleaning of filters in use and other demanding conditions.The improved microfiber and nanofiber performance is a result of theimproved character of the polymeric materials forming the microfiber ornanofiber. Further, the filter media of the invention using the improvedpolymeric materials of the invention provides a number of advantageousfeatures including higher efficiency, lower flow restriction, highdurability (stress related or environmentally related) in the presenceof abrasive particulates and a smooth outer surface free of loose fibersor fibrils. The overall structure of the filter materials provides anoverall thinner media allowing improved media area per unit volume,reduced velocity through the media, improved media efficiency andreduced flow restrictions.

The polymer can be an additive polymer, a condensation polymer ormixtures or blends thereof. A preferred mode of the invention is apolymer blend comprising a first polymer and a second, but differentpolymer (differing in polymer type, molecular weight or physicalproperty) that is conditioned or treated at elevated temperature. Thepolymer blend can be reacted and formed into a single chemical specie orcan be physically combined into a blended composition by an annealingprocess. Annealing implies a physical change, like crystallinity, stressrelaxation or orientation. Preferred materials are chemically reactedinto a single polymeric specie such that a Differential ScanningCalorimeter analysis reveals a single polymeric material. Such amaterial, when combined with a preferred additive material, can form asurface coating of the additive on the microfiber that providesoleophobicity, hydrophobicity or other associated improved stabilitywhen contacted with high temperature, high humidity and difficultoperating conditions. The fine fiber of the class of materials can havea diameter of 0.001 micron to 10 microns. Useful sizes include 0.001 to2 microns, 0.005 to 5 microns, 0.01 to 5 microns, depending on bonding,substrate and application. Such microfibers can have a smooth surfacecomprising a discrete layer of the additive material or an outer coatingof the additive material that is partly solubilized or alloyed in thepolymer surface, or both. Preferred materials for use in the blendedpolymeric systems include nylon 6; nylon 66; nylon 6-10; nylon(6-66-610) copolymers and other linear generally aliphatic nyloncompositions. A preferred nylon copolymer resin (SVP-651) was analyzedfor molecular weight by the end group titration. (J. E. Walz and G. B.Taylor, determination of the molecular weight of nylon, Anal. Chem. Vol.19, Number 7, pp 448–450 (1947). A number average molecular weight(M_(n)) was between 21,500 and 24,800. The composition was estimated bythe phase diagram of melt temperature of three component nylon, nylon 6about 45%, nylon 66 about 20% and nylon 610 about 25%. (Page 286, NylonPlastics Handbook, Melvin Kohan ed. Hanser Publisher, New York (1995)).

Reported physical properties of SVP 651 resin are:

Property ASTM Method Units Typical Value Specific Gravity D-792 — 1.08Water Absorption D-570 % 2.5 (24 hr immersion) Hardness D-240 Shore D 65Melting Point DSC ° C. (° F.) 154 (309) Tensile Strength D-638 MPa(kpsi)  50 (7.3) @ Yield Elongation at Break D-638 % 350 FlexuralModulus D-790 MPa (kpsi) 180 (26)  Volume Resistivity D-257 ohm-cm  10¹²

A polyvinylalcohol having a hydrolysis degree of from 87 to 99.9+% canbe used in such polymer systems. These are preferably cross linked. Andthey are most preferably crosslinked and combined with substantialquantities of the oleophobic and hydrophobic additive materials.

Another preferred mode of the invention involves a single polymericmaterial combined with an additive composition to improve fiber lifetimeor operational properties. The preferred polymers useful in this aspectof the invention include nylon polymers, polyvinylidene chloridepolymers, polyvinylidene fluoride polymers, polyvinylalcohol polymersand, in particular, those listed materials when combined with stronglyoleophobic and hydrophobic additives that can result in a microfiber ornanofiber with the additive materials formed in a coating on the finefiber surface. Again, blends of similar polymers such as a blend ofsimilar nylons, similar polyvinylchloride polymers, blends ofpolyvinylidene chloride polymers are useful in this invention. Further,polymeric blends or alloys of differing polymers are also contemplatedby the invention. In this regard, compatible mixtures of polymers areuseful in forming the microfiber materials of the invention. Additivecomposition such a fluoro-surfactant, a nonionic surfactant, lowmolecular weight resins (e.g.) tertiary butylphenol resin having amolecular weight of less than about 3000 can be used. The resin ischaracterized by oligomeric bonding between phenol nuclei in the absenceof methylene bridging groups. The positions of the hydroxyl and thetertiary butyl group can be randomly positioned around the rings.Bonding between phenolic nuclei always occurs next to hydroxyl group,not randomly. Similarly, the polymeric material can be combined with analcohol soluble non-linear polymerized resin formed from bis-phenol A.Such material is similar to the tertiary butylphenol resin describedabove in that it is formed using oligomeric bonds that directly connectaromatic ring to aromatic ring in the absence of any bridging groupssuch as alkylene or methylene groups.

Preferred polymer systems of the invention have adhering characteristicsuch that when contacted with a cellulosic substrate adheres to thesubstrate with sufficient strength such that it is securely bonded tothe substrate and can resist the delaminating effects of a reverse pulsecleaning technique and other mechanical stresses. In such a mode, thepolymer material must stay attached to the substrate while undergoing apulse clean input that is substantially equal to the typical filtrationconditions except in a reverse direction across the filter structure.Such adhesion can arise from solvent effects of fiber formation as thefiber is contacted with the substrate or the post treatment of the fiberon the substrate with heat or pressure. However, polymer characteristicsappear to play an important role in determining adhesion, such asspecific chemical interactions like hydrogen bonding, contact betweenpolymer and substrate occurring above or below Tg, and the polymerformulation including additives. Polymers plasticized with solvent orsteam at the time of adhesion can have increased adhesion.

An important aspect of the invention is the utility of such microfiberor nanofiber materials formed into a filter structure. In such astructure, the fine fiber materials of the invention are formed on andadhered to a filter substrate. Natural fiber and synthetic fibersubstrates, like spun bonded fabrics, non-woven fabrics of syntheticfiber and non-wovens made from the blends of cellulosics, synthetic andglass fibers, non-woven and woven glass fabrics, plastic screen likematerials both extruded and hole punched, UF and MF membranes of organicpolymers can be used. Sheet-like substrate or cellulosic non-woven webcan then be formed into a filter structure that is placed in a fluidstream including an air stream or liquid stream for the purpose ofremoving suspended or entrained particulate from that stream. The shapeand structure of the filter material is up to the design engineer. Oneimportant parameter of the filter elements after formation is itsresistance to the effects of heat, humidity or both. One aspect of thefilter media of the invention is a test of the ability of the filtermedia to survive immersion in warm water for a significant period oftime. The immersion test can provide valuable information regarding theability of the fine fiber to survive hot humid conditions and to survivethe cleaning of the filter element in aqueous solutions that can containsubstantial proportions of strong cleaning surfactants and strongalkalinity materials. Preferably, the fine fiber materials of theinvention can survive immersion in hot water while retaining at least30%, preferably 50% of the fine fiber formed on the surface of thesubstrate. Retention of at least 30%, preferably 50% of the fine fibercan maintain substantial fiber efficiency without loss of filtrationcapacity or increased back pressure. Most preferably retaining at least75%. The thickness of the typical fine fiber filtration layer rangesfrom about 1 to 100 times the fiber diameter with a basis weight rangingfrom about 0.01 to 240 micrograms-cm⁻².

Fluid streams such as air and gas streams often carry particulatematerial therein. The removal of some or all of the particulate materialfrom the fluid stream is needed. For example, air intake streams to thecabins of motorized vehicles, air in computer disk drives, HVAC air,aircraft cabin ventilation, clean room ventilation and applicationsusing filter bags, barrier fabrics, woven materials, air to engines formotorized vehicles, or to power generation equipment; gas streamsdirected to gas turbines; and, air streams to various combustionfurnaces, often include particulate material therein. In the case ofcabin air filters it is desirable to remove the particulate matter forcomfort of the passengers and/or for aesthetics. With respect to air andgas intake streams to engines, gas turbines and combustion furnaces, itis desirable to remove the particulate material because particulate cancause substantial damage to the internal workings to the variousmechanisms involved. In other instances, production gases or off gasesfrom industrial processes or engines may contain particulate materialtherein. Before such gases can be, or should be, discharged throughvarious downstream equipment to the atmosphere, it may be desirable toobtain a substantial removal of particulate material from those streams.

A general understanding of some of the basic principles and problems ofair filter design can be understood by consideration of the followingtypes of filter media: surface loading media; and, depth media. Each ofthese types of media has been well studied, and each has been widelyutilized. Certain principles relating to them are described, forexample, in U.S. Pat. Nos. 5,082,476; 5,238,474; and 5,364,456. Thecomplete disclosures of these three patents are incorporated herein byreference.

The “lifetime” of a filter is typically defined according to a selectedlimiting pressure drop across the filter. The pressure buildup acrossthe filter defines the lifetime at a defined level for that applicationor design. Since this buildup of pressure is a result of load, forsystems of equal efficiency a longer life is typically directlyassociated with higher capacity. Efficiency is the propensity of themedia to trap, rather than pass, particulates. It should be apparentthat typically the more efficient a filter media is at removingparticulates from a gas flow stream, in general the more rapidly thefilter media will approach the “lifetime” pressure differential(assuming other variables to be held constant).

DETAILED DESCRIPTION OF CERTAIN DRAWINGS

The microfiber or nanofiber of the unit can be formed by theelectrostatic spinning process. A suitable apparatus for forming thefiber is illustrated in FIG. 1. This apparatus includes a reservoir 80in which the fine fiber forming polymer solution is contained, a pump 81and a rotary type emitting device or emitter 40 to which the polymericsolution is pumped. The emitter 40 generally consists of a rotatingunion 41, a rotating portion 42 including a plurality of offset holes 44and a shaft 43 connecting the forward facing portion and the rotatingunion. The rotating union 41 provides for introduction of the polymersolution to the forward facing portion 42 through the hollow shaft 43.The holes 44 are spaced around the periphery of the forward facingportion 42. Alternatively, the rotating portion 42 can be immersed intoa reservoir of polymer fed by reservoir 80 and pump 81. The rotatingportion 42 then obtains polymer solution from the reservoir and as itrotates in the electrostatic field, a droplet of the solution isaccelerated by the electrostatic field toward the collecting media 70 asdiscussed below.

Facing the emitter 40, but spaced apart therefrom, is a substantiallyplanar grid 60 upon which the collecting media 70 (i.e. substrate orcombined substrate is positioned. Air can be drawn through the grid. Thecollecting media 70 is passed around rollers 71 and 72 which arepositioned adjacent opposite ends of grid 60. A high voltageelectrostatic potential is maintained between emitter 40 and grid 60 bymeans of a suitable electrostatic voltage source 61 and connections 62and 63 which connect respectively to the grid 60 and emitter 40.

In use, the polymer solution is pumped to the rotating union 41 orreservoir from reservoir 80. The forward facing portion 42 rotates whileliquid exits from holes 44, or is picked up from a reservoir, and movesfrom the outer edge of the emitter toward collecting media 70 positionedon grid 60. Specifically, the electrostatic potential between grid 60and the emitter 40 imparts a charge to the material which cause liquidto be emitted therefrom as thin fibers which are drawn toward grid 60where they arrive and are collected on substrate 12 or an efficiencylayer 14. In the case of the polymer in solution, solvent is evaporatedoff the fibers during their flight to the grid 60; therefore, the fibersarrive at the substrate 12 or efficiency layer 14. The fine fibers bondto the substrate fibers first encountered at the grid 60. Electrostaticfield strength is selected to ensure that the polymer material as it isaccelerated from the emitter to the collecting media 70, theacceleration is sufficient to render the material into a very thinmicrofiber or nanofiber structure. Increasing or slowing the advancerate of the collecting media can deposit more or less emitted fibers onthe forming media, thereby allowing control of the thickness of eachlayer deposited thereon. The rotating portion 42 can have a variety ofbeneficial positions. The rotating portion 42 can be placed in a planeof rotation such that the plane is perpendicular to the surface of thecollecting media 70 or positioned at any arbitrary angle. The rotatingmedia can be positioned parallel to or slightly offset from parallelorientation.

FIG. 2 is a general schematic diagram of a process and apparatus forforming a layer of fine fiber on a sheet-like substrate or media. InFIG. 2, the sheet-like substrate is unwound at station 20. Thesheet-like substrate 20 a is then directed to a splicing station 21wherein multiple lengths of the substrate can be spliced for continuousoperation. The continuous length of sheet-like substrate is directed toa fine fiber technology station 22 comprising the spinning technology ofFIG. 1 wherein a spinning device forms the fine fiber and lays the finefiber in a filtering layer on the sheet-like substrate. After the finefiber layer is formed on the sheet-like substrate in the formation zone22, the fine fiber layer and substrate are directed to a heat treatmentstation 23 for appropriate processing. The sheet-like substrate and finefiber layer is then tested in an efficiency monitor 24 and nipped ifnecessary at a nip station 25. The sheet-like substrate and fiber layeris then steered to the appropriate winding station to be wound onto theappropriate spindle for further processing 26 and 27.

FIG. 3 is a scanning electromicrograph image showing the relationship oftypical dust particles having a diameter of about 2 and about 5 micronswith respect to the sizes of pores in typical cellulose media and in thetypical fine fiber structures. In FIG. 3 a, the 2 micron particle 31 andthe 5 micron particle 32 is shown in a cellulosic media 33 with poresizes that are shown to be quite a bit larger than the typical particlediameters. In sharp contrast, in FIG. 3B, the 2 micron particle 31appears to be approximately equal to or greater than the typicalopenings between the fibers in the fiber web 35 while the 5 micronparticle 32 appears to be larger than any of the openings in the finefiber web 35.

The foregoing general description of the various aspects of thepolymeric materials of the invention, the fine fiber materials of theinvention including both microfibers and nanofibers and the constructionof useful filter structures from the fine fiber materials of theinvention provides an understanding of the general technologicalprinciples of the operation of the invention. The following specificexemplary materials are examples of materials that can be used in theformation of the fine fiber materials of the invention and the followingmaterials disclose a best mode. The following exemplary materials weremanufactured with the following characteristics and process conditionsin mind. Electrospinning small diameter fiber less than 10 micron isobtained using an electrostatic force from a strong electric fieldacting as a pulling force to stretch a polymer jet into a very finefilament. A polymer melt can be used in the electrospinning process,however, fibers smaller than 1 micron are best made from polymersolution. As the polymer mass is drawn down to smaller diameter, solventevaporates and contributes to the reduction of fiber size. Choice ofsolvent is critical for several reasons. If solvent dries too quickly,then fibers tends to be flat and large in diameter. If the solvent driestoo slowly, solvent will redissolve the formed fibers. Thereforematching drying rate and fiber formation is critical. At high productionrates, large quantities of exhaust air flow helps to prevent a flammableatmosphere, and to reduce the risk of fire. A solvent that is notcombustible is helpful. In a production environment the processingequipment will require occasional cleaning. Safe low toxicity solventsminimize worker exposure to hazardous chemicals. Electrostatic spinningcan be done at a flow rate of 1.5 ml/min per emitter, a target distanceof 8 inches, an emitter voltage of 88 kV, an emitter rpm of 200 and arelative humidity of 45%.

The choice of polymer system is important for a given application. Forpulse cleaning application, an extremely thin layer of microfiber canhelp to minimize pressure loss and provide an outer surface for particlecapture and release. A thin layer of fibers of less than 2-microndiameter, preferably less than 0.3-micron diameter is preferred. Goodadhesion between microfiber or nanofiber and substrates upon which themicrofibers or nanofibers are deposited is important. When filters aremade of composites of substrate and thin layer of micro- and nanofibers,such composite makes an excellent filter medium for self-cleaningapplication. Cleaning the surface by back pulsing repeatedly rejuvenatesthe filter medium. As a great force is exerted on the surface, finefiber with poor adhesion to substrates can delaminate upon a back pulsethat passes from the interior of a filter through a substrate to themicro fiber. Therefore, good cohesion between micro fibers and adhesionbetween substrate fibers and electrospun fibers is critical forsuccessful use.

Products that meet the above requirements can be obtained using fibersmade from different polymer materials. Small fibers with good adhesionproperties can be made from such polymers like polyvinylidene chloride,poly vinyl alcohol and polymers and copolymers comprising various nylonssuch as nylon 6, nylon 4,6; nylon 6,6; nylon 6,10 and copolymersthereof. Excellent fibers can be made from PVDF, but to makesufficiently small fiber diameters requires chlorinated solvents. Nylon6, Nylon 66 and Nylon 6,10 can be electrospun. But, solvents such asformic acid, m-cresol, tri-fluoro ethanol, hexafluoro isopropanol areeither difficult to handle or very expensive. Preferred solvents includewater, ethanol, isopropanol, acetone and N-methyl pyrrolidone due totheir low toxicity. Polymers compatible with such solvent systems havebeen extensively evaluated. We have found that fibers made from PVC,PVDC, polystyrene, polyacrylonitrile, PMMA, PVDF require additionaladhesion means to attain structural properties. We also found that whenpolymers are dissolved in water, ethanol, isopropanol, acetone, methanoland mixtures thereof and successfully made into fibers, they haveexcellent adhesion to the substrate, thereby making an excellent filtermedium for self-cleaning application. Self-cleaning via back air pulseor twist is useful when filer medium is used for very high dustconcentration. Fibers from alcohol soluble polyamides and poly(vinylalcohol)s have been used successfully in such applications. Examples ofalcohol soluble polyamides include Macromelt 6238, 6239, and 6900 fromHenkel, Elvamide 8061 and 8063 from duPont and SVP 637 and 651 fromShakespeare Monofilament Company. Another group of alcohol solublepolyamide is type 8 nylon, alkoxy alkyl modifies nylon 66 (Ref. Page447, Nylon Plastics handbook, Melvin Kohan ed. Hanser Publisher, NewYork, 1995). Examples of poly(vinyl alcohol) include PVA-217, 224 fromKuraray, Japan and Vinol 540 from Air Products and Chemical Company.

We have found that filters can be exposed to extremes in environmentalconditions. Filters in Saudi Arabian desert can be exposed totemperature as high as 150° F. or higher. Filters installed in Indonesiaor Gulf Coast of US can be exposed high humidity above 90% RH and hightemperature of 100° F. Or, they can be exposed to rain. We have foundthat filters used under the hood of mobile equipment like cars, trucks,buses, tractors, and construction equipment can be exposed to hightemperature (+200° F.), high relative humidity and other chemicalenvironment. We have developed test methods to evaluate survivability ofmicrofiber systems under harsh conditions. Soaking the filter mediasamples in hot water (140° F.) for 5 minutes or exposure to highhumidity, high temperature and air flow.

B. General Principles Relating to Air Cleaner Design

Herein, the term “air cleaner” will be used in reference to a systemwhich functions to remove particulate material from an air flow stream.The term “air filter” references a system in which removal is conductedby passage of the air, carrying particulate therein, through filtermedia. The term “filter media” or “media” refers to a material orcollection of material through which the air passes, with a concomitantdeposition of the particles in or on the media. The term “surfaceloading media” or “barrier media” refers to a system in which as the airpasses through the media, the particulate material is primarilydeposited on the surface of the media, forming a filter cake, as opposedto into or through the depth of the media.

Herein the term “filter element” is generally meant to refer to aportion of the air cleaner which includes the filter media therein. Ingeneral, a filter element will be designed as a removable andreplaceable, i.e. serviceable, portion of the air cleaner. That is, thefilter media will be carried by the filter element and be separable fromthe remainder portion of the air cleaner so that periodically the aircleaner can be rejuvenated by removing a loaded or partially loadedfilter element and replacing it with a new, or cleaned, filter element.Preferably, the air cleaner is designed so that the removal andreplacement can be conducted by hand. By the term “loaded” or variantsthereof in this context, reference is meant to an air cleaner which hasbeen on-line a sufficient period of time to contain a significant amountof trapped particles or particulates thereon. In many instances, duringnormal operation, a filter element will increase in weight, due toparticulate loading therein, of two or three times (or more) itsoriginal weight.

In general, specifications for the performance of an air cleaner systemare, generated by the preferences of the original equipment manufacturer(OEM) for the engine involved and/or the OEM of the truck or otherequipment involved. While a wide variety of specifications may beinvolved, some of the major ones are the following:

-   -   1. Engine air intake need (rated flow)    -   2. Initial Restriction    -   3. Initial efficiency    -   4. Average or overall operating restriction    -   5. Overall efficiency    -   6. Filter service life

The engine air intake need is a function of the engine size, i.e.displacement and rpm at maximum, full or “rated” load. In general, it isthe product of displacement and rated rpm, modified by the volumetricefficiency, a factor which reflects turbo efficiency, duct efficiency,etc. In general, it is a measurement of the volume of air, per unittime, required by the engine or other system involved, during ratedoperation or full load. While air intake need will vary depending uponrpm, the air intake requirement is defined at a rated rpm, often at 1800rpm or 2100 rpm for many typical truck engines. Herein this will becharacterized as the “rated air flow” or by similar terms. In general,principles characterized herein can be applied to air cleanerarrangements used with systems specified for operation over a wide rangeof ratings or demands, including, for example, ones in the range ofabout 3 cubic feet/min. (cfm) up to 10,000 cfm often 50 to 500 cfm. Suchequipment includes, for example: small utility engines (motorcycles,lawn mowers, etc.), automotive engines, pickup trucks and sport utilityvehicle engines, engines for small trucks and delivery vehicles, buses,over-the-highway trucks, agricultural equipment (for example tractors),construction equipment, mining equipment, marine engines, a variety ofgenerator engines, and, in some instances, gas turbines and aircompressors.

Air cleaner overall efficiency is generally a reflection of the amountof “filterable” solids which pass into the air cleaner during use, andwhich are retained by the air cleaner. It is typically represented asthe percentage of solids passing into the air cleaner which are retainedby the air cleaner in normal use, on a weight basis. It is evaluated andreported for many systems by using SAE standards, which techniques aregenerally characterized in U.S. Pat. No. 5,423,892 at Column 25, line60–Column 26, line 59; Column 27, lines 1–40. A typical standard used isSAE J726, incorporated herein by reference.

With respect to efficiency, engine manufacturer and/or equipmentmanufacturer specifications will vary, in many instances, withefficiency demands (based on either SAE J726 or field testing) foroverall operation often being set at 99.5% or higher, typically at 99.8%or higher. With typical vehicle engines having air flow demands of 500cfm or above, specifications of 99.8% overall average, or higher, arenot uncommon.

Initial efficiency is the measurable efficiency of the filter when it isfirst put on line. As explained in U.S. Pat. No. 5,423,892 at Column 27,lines 1–40, especially with conventional pleated paper (barrier type orsurface-loading) filters, initial efficiency is generally substantiallylower than the overall average efficiency during use. This is becausethe “dust cake” or contaminant build-up on the surface of such a filterduring operation, increases the efficiency of the filter. Initialefficiency is also often specified by the engine manufacturer and/or thevehicle manufacturer. With typical vehicle engines having air flowdemands of 500 cfm or above, specifications of 98% or above (typically98.5% or above) are common.

Restriction is the pressure differential across an air cleaner or aircleaner system during operation. Contributors to the restrictioninclude: the filter media through which the air is directed; duct sizethrough which the air is directed; and, structural features againstwhich or around which the air is directed as it flows through the aircleaner and into the engine. With respect to air cleaners, initialrestriction limits are often part of the specifications and demands ofthe engine manufacturer and/or equipment manufacturer. This initialrestriction would be the pressure differential measured across the aircleaner when the system is put on line with a clean air filter thereinand before significant loading occurs. Typically, the specifications forany given system have a maximum initial restriction requirement.

In general, engine and equipment manufacturers design equipment withspecifications for air cleaner efficiency up to a maximum restriction.As reported in U.S. Pat. No. 5,423,892, at Column 2, lines 19–29; and,column 6, line 47, column 7, line 3, the limiting restriction: fortypical truck engines is a pressure drop of about 20–30 inches of water,often about 25 inches of water; for automotive internal combustionengines is about 20–25 inches of water; for gas turbines, is typicallyabout 5 inches of water; and, for industrial ventilation systems, istypically about 3 inches of water.

In general, some of the principal variables of concern in air cleanerdesign in order to develop systems to meet the types of specificationscharacterized in the previous section, are the following:

-   -   1. filter media type, geometry and efficiency;    -   2. air cleaner shape and structure; and    -   3. filter element size.

For example, conventional cellulose fiber media or similar media isgenerally a “barrier” filter. An example is paper media. In general, theoperation of such media is through surface loading, i.e., when air isdirected through the media, the surface of the media acts as a barrieror sieve, preventing passage of particulate material therethrough. Intime, a dust cake builds on the surface of the media, increasing mediaefficiency. In general, the “tightness” or “porosity” of the fiberconstruction determines the efficiency, especially the initialefficiency, of the system. In time, the filter cake will effect(increase) the efficiency.

In general, such media is often defined or specified by itspermeability. The permeability test for media is generally characterizedin U.S. Pat. No. 5,672,399 at Col. 19, lines 27–39. In general, it isthe media face velocity (air) required to induce a 0.50 inch waterrestriction across a flat sheet of the referenced material, media orcomposite. Permeability, as used herein, is assessed by a Frazier PermTest, according to ASTM D737 incorporated herein by reference, forexample using a Frazier Perm Tester available from Frazier PrecisionInstrument Co., Inc., Gaithersburg, Md., or by some analogous test.

The permeability of cellulose fiber media used in many types of enginefilters for trucks having rated air flows of 50 cfm or more manufacturedby Donaldson Company, is media having a permeability of less than about15 fpm, typically around 13 fpm. In general, in the engine filtrationmarket, for such equipment, a variety of barrier media (pleated media)having permeability values of less than about 25 fpm, and typicallysomewhere within the range of 10–25 fpm, have been widely utilized byvarious element manufacturers.

With respect to efficiency, principles vary with respect to the type ofmedia involved. For example, cellulose fiber or similar barrier media isgenerally varied, with respect to efficiency, by varying overall generalporosity or permeability.

C. Typical System; Engine Air Intake

In FIG. 21, a schematic view of a system is shown generally at 130.System 130 is one example type of system in which air cleanerarrangements and constructions described herein is usable. In FIG. 21,equipment 131, such as a vehicle, having an engine 132 with some definedrated air flow demand, for example, at least 370 cfm, is shownschematically. Equipment 131 may comprise a bus, an over the highwaytruck, an off-road vehicle, a tractor, or marine application such as apower boat. Engine 132 powers equipment 131, through use of an air, fuelmixture. In FIG. 21, air flow is shown drawn into engine 132 at anintake region 133. An optional turbo 134 is shown in phantom, asoptionally boosting the air intake into the engine 132. An air cleaner135 having a media pack 136 is upstream of the engine 132 and turbo 134.In general, in operation, air is drawn in at arrow 137 into the aircleaner 135 and through media pack 136. There, particles andcontaminants are removed from the air. The cleaned air flows at arrow137 into the intake 133. From there, the air flows into engine 132, topower vehicle 131.

In engine systems, during operation of the engine, the temperature,under the hood, typically is at least 120° F., and often is in the rangeof 140° F.–220° F. or more depending on operating conditions. Thetemperature may adversely affect the operating efficiency of the filterelement. Regulations on emissions can increase the restriction on theengine exhaust, causing further increased temperatures. As explainedbelow, constructing the filter media in the form of a composite of abarrier media and at least a single layer, and in some instances,multiple layers of “fine fiber” can improve the performance (theoperating efficiency, in particular) of the filter element over priorart filter elements that are not constructed from such media composites.

D. Example Air Cleaners

Attention is directed to FIG. 22. FIG. 22 is a perspective view of afirst embodiment of a media pack 140. The preferred media pack 140depicted includes filter media 142 and a sealing system 144. Inpreferred constructions, the filter media 142 is designed to removeparticulates from a fluid, such as air, passing through the filter media142, while the sealing system 144 is designed to seal the media pack 140against a sidewall of a housing or duct, as shown in FIG. 24.

This media pack 140 of FIGS. 22–25 is generally described in U.S. Pat.No. 6,190,432, which is incorporated by reference herein.

In certain preferred arrangements, the filter media 142 will beconfigured for straight-through flow. By “straight-through flow,” it ismeant that the filter media 142 is configured in a construction 146 witha first flow face 148 (corresponding to an inlet end, in the illustratedembodiment) and an opposite, second flow face 150 (corresponding to anoutlet end, in the illustrated embodiment), with fluid flow entering inone direction 152 through the first flow face 148 and exiting in thesame direction 154 from the second flow face 150. When used with aninline-flow housing, in general, the fluid will enter through the inletof the housing in one direction, enter the filter construction 146through the first flow face 148 in the same direction, exit the filterconstruction 146 in the same direction from the second flow face 150,and exit the housing through the housing outlet also in the samedirection.

In FIG. 22, the first flow face 148 and the second flow face 150 aredepicted as planar and as parallel. In other embodiments, the first flowface 148 and the second flow face 150 can be non-planar, for example,frusto-conical. Further, the first flow face 148 and second flow face150 need not be parallel to each other.

Generally, the filter construction 146 will be a wound construction.That is, the construction 146 will typically include a layer of filtermedia that is turned completely or repeatedly about a center point.Typically, the wound construction will be a coil, in that a layer offilter media will be rolled a series of turns around a center point. Inarrangements where a wound, coiled construction is used, the filterconstruction 146 will be a roll of filter media, typically permeablefluted filter media.

Attention is now directed to FIG. 23. FIG. 23 is schematic, perspectiveview demonstrating the principles of operation of certain preferredmedia usable in the filter constructions herein. In FIG. 23, a flutedconstruction of Z-media is generally designated at 156. Preferably, thefluted construction 156 includes: a layer 157 of corrugations having aplurality of flutes 158 and a face sheet 160. The FIG. 22 embodimentshows two sections of the face sheet 160, at 160A (depicted on top ofthe corrugated layer 157) and at 160B (depicted below the corrugatedlayer 157). Typically, the preferred media construction 162 used inarrangements described herein will include the corrugated layer 157secured to the bottom face sheet 160B. When using this mediaconstruction 162 in a rolled construction, it typically will be woundaround itself, such that the bottom face sheet 160B will cover the topof the corrugated layer 157. The face sheet 160 covering the top of thecorrugated layer is depicted as 160A. It should be understood that theface sheet 160A and 160B are the same sheet 160.

When using this type of media construction 162, the flute chambers 158preferably form alternating peaks 164 and troughs 166. The troughs 166and peaks 164 divide the flutes into an upper row and lower row. In theparticular configuration shown in FIG. 23, the upper flutes form flutechambers 168 closed at the downstream end 178, while flute chambers 170having their upstream end 181 closed form the lower row of flutes. Thefluted chambers 170 are closed by a first end bead 172 that fills aportion of the upstream end 181 of the flute between the fluting sheet171 and the second facing sheet 160B. Similarly, a second end bead 174closes the downstream end 178 of alternating flutes 168.

When using media constructed in the form of media construction 162,during use, unfiltered fluid, such as air, enters the flute chambers 168as indicated by the shaded arrows 176. The flute chambers 168 have theirupstream ends 169 open. The unfiltered fluid flow is not permitted topass through the downstream ends 178 of the flute chambers 168 becausetheir downstream ends 178 are closed by the second end bead 174.Therefore, the fluid is forced to proceed through the fluting sheet 171or face sheets 160. As the unfiltered fluid passes through the flutingsheet 171 or face sheets 160, the fluid is cleaned or filtered. Thecleaned fluid is indicated by the unshaded arrow 180. The fluid thenpasses through the flute chambers 170 (which have their upstream ends181 closed) to flow through the open downstream end 184 out the flutedconstruction 156. With the configuration shown, the unfiltered fluid canflow through the fluted sheet 171, the upper facing sheet 160A, or lowerfacing sheet 160B, and into a flute chamber 170.

Typically, the media construction 162 will be prepared and then wound toform a rolled construction 146 of filter media. When this type of mediais selected for use, the media construction 162 prepared includes thesheet of corrugations 157 secured with the end bead 172 to the bottomface sheet 160B (as shown in FIG. 23, but without the top face sheet160A).

Attention is again directed to FIG. 22. In FIG. 22, the second flow face150 is shown schematically. There is a portion at 182 in which theflutes including the open ends 184 and closed ends 178 are depicted. Itshould be understood that this section 182 is representative of theentire flow face 50. For the sake of clarity and simplicity, the flutesare not depicted in the other remaining portions 183 of the flow face150. Top and bottom plan views, as well as side elevational views of amedia pack 140 usable in the systems and arrangements described hereinare depicted in copending and commonly assigned U.S. patent applicationSer. No. 29/101,193, filed Feb. 26, 1999, and entitled, “Filter ElementHaving Sealing System,” herein incorporated by reference.

Turning now to FIG. 24, the filter construction 146 is shown installedin a housing 186 (which can be part of an air intake duct into an engineor turbo of an air cleaner 179). In the arrangement shown, air flowsinto the housing 186 at 187, through the filter construction 146, andout of the housing 186 at 188. When media constructions such as filterconstructions 46 of the type shown are used in a duct or housing 186,the sealing system 144 will be needed to ensure that air flows throughthe media construction 146, rather than bypass it.

The particular sealing system 144 depicted includes a frame construction190 and a seal member 192. When this type of sealing system 144 is used,the frame construction 190 provides a support structure or backingagainst which the seal member 192 can be compressed against to form aradial seal 194 with the duct or housing 186.

Still in reference to FIG. 24, in the particular embodiment shown, theframe construction 190 includes a rigid projection 196 that projects orextends from at least a portion of one of the first and second flowfaces 148, 150 of the filter construction 146. The rigid projection 196,in the particular arrangement shown in FIG. 24, extends axially from thesecond flow face 150 of the filter construction 146.

The projection 196 shown has a pair of opposite sides 198, 102 joined byan end tip 104. In preferred arrangements, one of the first and secondsides 198, 102 will provide a support or backing to the seal member 192such that seal 194 can be formed between and against the selected side198 or 102 and the appropriate surface of the housing or duct. When thistype of construction is used, the projection 196 will be a continuousmember forming a closed hoop structure 106 (FIG. 22).

When this type of construction is used, a housing or duct maycircumscribe the projection 196 and hoop structure 106 including theseal member 192 to form seal 194 between and against the outer side 102of the projection 196 and an inner surface 110 of the housing or duct.

In the particular embodiment shown in FIG. 24, the seal member 192engages the end tip 104 of the projection 196 as well, such that theseal member 192 covers the projection 196 from the exterior side 102,over the end tip 104, and to the interior side 198.

Referring now to FIGS. 22 and 24, the frame 190 has a band, skirt, ordepending lip 107 that is used to secure the frame 190 to the mediaconstruction 146. The depending lip 107 depends or extends down a firstdistance from cross braces 108.

During use of frames 190 of the type depicted herein, inward forces areexerted around the circumference of the frame 190. Cross braces 108support the frame 190. By the term “support,” it is meant that the crossbraces 108 prevent the frame 190 from radially collapsing under theforces exerted around the circumference of the frame 190.

The tip portion 104 provides support for the compressible seal member192. The compressible seal member 192 is preferably constructed andarranged to be sufficiently compressible to be compressed between thetip portion 104 of the frame 190 and sidewall 110 of a housing or duct.When sufficiently compressed between the tip portion 104 and thesidewall 110, radial seal 194 is formed between the media pack 140 andthe sidewall 110.

One preferred configuration for seal member 192 is shown in FIG. 25. Thetip portion 104 of the frame 190 defines a wall or support structurebetween and against which radial seal 194 may be formed by thecompressible seal member 192. The compression of the compressible sealmember 192 at the sealing system 144 is preferably sufficient to form aradial seal under insertion pressures of no greater than 80 lbs.,typically, no greater than 50 lbs., for example, about 20–40 lbs., andlight enough to permit convenient and easy change out by hand.

In the preferred embodiment shown in FIG. 25, the seal member 192 is astepped cross-sectional configuration of decreasing outermost dimensions(diameter, when circular) from a first end 112 to a second end 113, toachieve desirable sealing. Preferred specifications for the profile ofthe particular arrangement shown in FIG. 25 are as follows: apolyurethane foam material having a plurality of (preferably at leastthree) progressively larger steps configured to interface with thesidewall 110 and provide a fluid-tight seal.

The compressible seal member 192 defines a gradient of increasinginternal diameters of surfaces for interfacing with the sidewall 110.Specifically, in the example shown in FIG. 25, the compressible sealmember 192 defines three steps 114, 115, 116. The cross-sectionaldimension or width of the steps 114, 115, 116 increases the further thestep 114, 115, 116 is from the second end 113 of the compressible sealmember 192. The smaller diameter at the second end 113 allows for easyinsertion into a duct or housing. The larger diameter at the first end112 ensures a tight seal.

In general, the media pack 140 can be arranged and configured to bepress-fit against the sidewall 110 of the housing 186 or duct. In thespecific embodiment shown in FIG. 24, the compressible seal member 192is compressed between the sidewall 110 and the tip portion 104 of theframe 190. After compression, the compressible seal member 192 exerts aforce against the sidewall 110 as the compressible seal member 192 triesto expand outwardly to its natural state, forming radial seal 94 betweenand against the tip portion 104 and the sidewall 110.

A variety of housings are usable with the media pack 140. In theparticular embodiment depicted in FIG. 24, the housing 186 includes abody member or a first housing compartment 118 and a removable cover orsecond housing compartment 120. In some arrangements, the first housingcompartment 118 is affixed to an object, such as a truck. The secondhousing compartment 120 is removably secured to the first housingcompartment 118 by a latching device 122.

In the illustrated embodiment in FIG. 24, the second end 150 of themedia pack 140 with the attached frame 190 and compressible seal member192 is inserted into the first housing compartment 118. The media pack140 is press-fit into the first housing compartment 118 such that thecompressible seal member 192 is compressed between and against the tipportion 104 of the frame 190 and the sidewall 110 of the first housingcompartment 118, to form radial seal 194 therebetween.

During use of the arrangement depicted in FIG. 24, the fluid enters thehousing assembly 185 at the inlet region 124 of the second housingcompartment 120, in the direction shown at 187. The fluid passes throughthe filter construction 146. As the fluid passes through the filterconstruction 146, contaminants are removed from the fluid. The fluidexits the housing assembly 185 at the outlet region 128, in thedirection of 188. The compressible seal member 192 of the sealing system144 forms radial seal 194 to prevent contaminated fluid from exiting thehousing assembly 185, without first passing through the filterconstruction 146.

FIG. 26 is a perspective view of another embodiment of a media pack 130.In the construction depicted, the media pack 130 includes filter media132 and a sealing system 134. The filter media 132 is designed to removecontaminants from a fluid, such as air, passing through the filter media132. The sealing system 134 is designed to seal the filter media 134 toa housing or duct.

The construction and geometry of the media pack 130 of FIGS. 26–27, withthe exception of preferred media formulations given in Section H below,is described in U.S. Pat. No. 6,190,432, which is incorporated byreference herein.

In certain preferred arrangements, the filter media 132 will beconfigured in a filter construction 136 with a first flow face 138 andan opposite, second flow face 140.

The filter construction 136 can have a variety of configurations andcross-sectional shapes. In the particular embodiment illustrated in FIG.26, the filter construction 136 has a non-circular cross-section. Inparticular, the FIG. 26 embodiment of the filter construction 136 has anob-round or “racetrack” cross-sectional shape. By “racetrack”cross-sectional shape, it is meant that the filter construction 136includes first and second semicircular ends 141, 142 joined by a pair ofstraight segments 143, 144.

In FIG. 26, certain portions 146 are depicted showing the flutes,including the open and closed ends. It should be understood that thisportion or section 146 is representative of the entire flow face 140 (aswell as the first flow face 138). For the sake of clarity andsimplicity, the flutes are not depicted in the other remaining portions149 of the flow face 140. Top and bottom plan views, as well as sideelevational views of the media pack 130 usable in the systems andarrangements described herein are depicted in copending and commonlyassigned U.S. patent application Ser. No. 29/101,193, filed Feb. 26,1999, and entitled, “Filter Element Having Sealing System,” herein andincorporated by reference.

As with the embodiment of FIG. 22, the media pack 130 includes sealingsystem 134. In preferred constructions, the sealing system 134 includesa frame 148 and a seal member 150.

The frame 148 has a non-circular, for example, obround and inparticular, a racetrack shape and is arranged and configured forattachment to the end of the filter media 132. In particular, the frame148 has a band or skirt or depending lip 151 that is generally racetrackshaped. The depending lip 151 depends or extends down a distance fromcross braces 152 and is used to secure the frame 148 to the media pack130.

During use of the arrangements depicted, inward forces are exertedaround the circumference of the frame 148. Inward forces exerted againstthe semicircular ends 141, 142 can cause the straight segments 143, 144to bow or bend. Cross braces 152 are provided to provide structuralrigidity and support to the straight segments 143, 144. As can be seenin FIG. 26, the particular cross braces 152 depicted form a truss system154 between the opposing straight segments 143, 144. The truss system154 includes a plurality of rigid struts 156, preferably molded as asingle piece with the remaining portions of the frame 148.

The frame 148 is constructed analogously to the frame 90. As such, theframe 148 includes a tip portion 158 (FIG. 27). In preferredarrangements, the tip portion 158 acts as an annular sealing support. Inpreferred systems, the compressible seal member 150 has structureanalogous to the that of the compressible seal member 92 of FIG. 5.

Preferably, the media pack 130 will be installed in a duct or an aircleaner housing. In FIG. 27, the housing depicted is a two-piece housingincluding a cover 160 and a body member 162. The cover 160 defines anairflow inlet 164. The body member 162 defines an airflow outlet 166.The housing further includes a pre-cleaner arrangement 167 upstream ofthe media pack 130, such as that described in U.S. Pat. Nos. 2,887,177and 4,162,906, incorporated by reference herein. In the one depicted,the pre-cleaner arrangement 167 is in the cover 160. The cover 160includes a dust ejector 168 that expels dust and debris collected in thepre-cleaner 167.

The compressible seal member 150 is compressed between the sidewall 170and the tip portion 158 of the frame 150. As the media pack 130 ispress-fit, the compressible seal member 150 is compressed between andagainst the frame 148 (specifically, in the particular embodiment shown,the tip portion 158) and the sidewall 170. After compression, thecompressible seal member 150 exerts a force against the sidewall 170 asthe compressible seal member 150 tries to expand outwardly to itsnatural state, forming a radial seal 171 with the sidewall 170.

Preferred formulations for media 132 are described in Section H, below.

Another filter arrangement is shown in FIG. 28, generally at 174. Withthe exception of preferred media formulations described in Section Hbelow, the filter arrangement 174 is described in U.S. Pat. No.5,820,646, incorporated by reference herein.

The filter arrangement 174 includes a media pack 176 mounted in, held byand supported by a panel construction 178. Filter arrangement 174 alsoincludes a housing 180, which includes a body 181 and a removable covermember 182. The panel construction 178 holding the media pack 176 sealswithin the housing 180, and is removable and replaceable therefrom.

The media pack 176 includes fluted filter media 184 constructed asdescribed above with respect to FIG. 23.

E. Typical System; Gas Turbine Air Intake

In FIG. 29, the air intake of a gas turbine system is shown generally at200. Airflow is shown drawn into an air intake system 200 at arrows 201.The air intake system 200 includes a plurality of air filterarrangements 202 generally held in a tube sheet 203. In preferredsystems, the tube sheet 203 will be constructed to hold the filterarrangements 202 at an angle, relative to a vertical axis. Preferredangles will be between 5–25°, for example, about 7°. This permits liquidto drain from the filter arrangements 202 when the system 200 is notoperating.

The air is cleaned in the air filter arrangements 202, and then it flowsdownstream at arrows 204 into gas turbine generator 205, where it isused to generate power.

In FIG. 33, an example of the air intake of a microturbine isillustrated generally at 210. In general, microturbines are smallerversions of gas turbines typically used as stand-by generators. In someinstances, such microturbines are approximately 24 inches by 18 inchesand have electrical power output typically between 30 kilowatts and 100kilowatts. These systems typically have air flow between 1000 cfm and10,000 cfm.

In FIG. 33, airflow is shown drawn into an air intake system 211 atarrows 212. The air intake system 211 includes a filter arrangement 213.As the air is drawn through the filter arrangement 213, the air iscleaned in the air filter arrangement 213, and then flows downstream atarrows 214 into a gas turbine 215. The gas turbine then typically powersan electrical generator, a fluid compressor, or a fluid pump. Asexplained below, constructing the filter arrangement in the form of acomposite of a barrier media and at least a single layer, and in someinstances, multiple layers of “fine fiber” can improve the performance(the operating efficiency, in particular) of the filter arrangement overprior art filters that are not constructed from such media composites.

F. Example Filter Arrangements for Gas Turbine Systems

One example of an air filter arrangement 202 usable in system 200 orsystem 210 is shown in FIGS. 30–32. Other than preferred mediaformulations given in Section H, the air filter arrangement 202 isdescribed in commonly assigned U.S. Ser. No. 09/437,867, filed Nov. 10,1999, incorporated by reference herein. In general, the air filterarrangement 202 includes a first, or primary filter element 220 (FIGS.30 and 32) and a second filter element 222 (FIGS. 31 and 32), which actsas a prefilter. By the term “prefilter”, it is meant a separator that ispositioned upstream of the main, primary filter element 220, thatfunctions to remove large particles from the gas stream. The primaryfilter element 220 and the prefilter element 222 are preferably securedwithin a sleeve member 224 that is removably mountable in an aperture226 in tube sheet 203. In general, air flow is taken into the system 200and flows first through the prefilter element 222 and then through theprimary filter element 220. After exiting the primary filter element220, the air is directed into the generator 205.

In general, the element 220 is constructed from fluted or z-shaped media230, as described above in connection with FIGS. 2 and 3. In FIG. 30, itshould be understood that the outlet face 228 is shown schematically.That is, only a portion of the face 228 is shown with flutes. It shouldbe understood that, in typical systems, the entire face 228 will befluted.

The filter element 220 has a first end 232 and an opposite, second end234. In the arrangement depicted in FIG. 30, the first end 232 willcorrespond to an upstream end inlet face 227, while the second end 234will correspond to a downstream end outlet face 228. The straightthrough flow allows gas to flow into the first end 232 and exit thesecond end 234, such that the direction of the air flow into the firstend 232 is the same direction of air flow that is exiting the second end234. Straight through flow patterns can reduce the amount of turbulencein the gas flow.

The media 230 can be a polyester synthetic media, a media made fromcellulose, or blends of these types of materials and treated with finefiber.

Preferably, the prefilter element 222 is a pleated construction 236comprising a plurality of individual pleats 237. The pleats 237 arearranged in a zig-zag fashion. Preferred prefilter elements 222 willhave a generally circular cross-section.

The prefilter element 222 is configured to permit straight through flow.In other words, the air flows directly through the prefilter element222, entering at an inlet face 238 and exiting at an oppositely disposedoutlet face 239, wherein the direction of fluid flow entering the inletface 238 is in the same direction of fluid flow exiting the outlet face239.

In certain preferred embodiments, there will be at least 15 pleats 237,no greater than 80 pleats 237, and typically 30–50 pleats 237. Thepleated construction 236 is made from a media 240 that is folded in theform of pleats 237 centered around a central core 241. Useable types ofmedia 240 includes fiberglass, or alternatively, an air laid media.Specific properties of usable media 240 include: a dry laid filtermedium made from polyester fibers randomly oriented to form a web havinga weight of 2.7–3.3 oz./yd³ (92–112 g/m³); a free thickness (i.e.,thickness at 0.002 psi compression) of 0.25–0.40 in. (6.4–10.2 mm); anda permeability of at least 400 ft./min (122 m/min).

In general, the prefilter element 222 is removably and replaceablymountable in the sleeve member 224. The sleeve member 224 is describedin further detail below. In certain systems, the prefilter element 222is held within the sleeve member 224 by squeezing or compressing endtips of the media 240 against the inside wall of the sleeve member 224.

Preferred filter arrangements 202 constructed according to principlesherein will have sleeve member 224 secured to and circumscribing theprimary filter element 220. In general, the sleeve member 224 functionsto hold the primary element 220 in place in the system 200. Preferredsleeve members 224 will also hold the prefilter element 222 in placeupstream of the primary element 220.

As can be seen in FIGS. 30 and 31, the sleeve member 224 preferably hasa cross-section that matches the cross-section of the primary filterelement. The sleeve member 224 includes a surrounding wall 244 that iscurved in a form to result in a surrounding ring 245. The sleeve member224 is preferably oriented relative to the primary filter element 220 toextend at least 30% of the axial length of the primary filter element220. In many typical arrangements, the sleeve member 224 will extendgreater than 50% of the axial length of the primary filter element 220.Indeed, in most preferred arrangements, the sleeve member 224 willextend at least the entire length (that is, 100%) of the axial length ofthe primary filter element 220. In many typical applications, the sleevemember 224 will have a radius of at least 10 inches, typically 15–30inches, and in some instances, no greater than 50 inches.

The sleeve member 224 is preferably constructed and arranged with asealing system to allow for securing the primary filter element 220 tothe tube sheet 203, to inhibit air from bypassing the primary element220. In the illustrated embodiment, the sleeve member 224 includes aseal member pressure flange 246. The flange 246 at least partially, andin many embodiments fully, circumscribes the wall 244 of the sleevemember 224. The seal member pressure flange 246 operates as a backstopto support a seal member 248 in order to create a seal 250 between andagainst the flange 246 and the tube sheet 203. The flange 246 extendsradially from the wall 244 of the sleeve member 224 and fullycircumscribes the seal member 224. The flange 246 will extend radiallyfrom the wall 244 a distance sufficient to support the seal member 248.

A patch or retaining clip 252 (FIG. 30) extends over a joint 254 tosecure the sleeve member 224 in its final configuration Preferably, theretaining clip 252 is secured in a permanent way to the sleeve member224; for example, by ultrasonic welding.

Attention is directed to FIG. 32. It can be seen that the flange 246supports the seal member 248 on the axial side 256. The seal member 248generally comprises a circular gasket 258. The gasket 258 is preferablysecured to the flange 246, by adhesive between the gasket 258 and theside 256 of the flange 246. The gasket 258 is positioned on the flange246, such that the gasket 258 completely circumscribes the wall 244 andthe primary element 220.

The arrangement depicted also includes a system for clamping the sleevemember 224 to the tube sheet 203. In the illustrated embodiment, theclamping system includes a plurality of latches or clamps 260. Thereshould be enough latches or clamps 260 to form a good, tight seal 250between the flange 246 and the tube sheet 203, when the sleeve member224 is operably installed in the tube sheet 203; for example,illustrated is 4 clamps 260. In FIG. 32, the clamp 260 is shown incross-section. Each of the clamps 260 includes a lever 261, a nose 262,and a plate 263. The plate 263 includes apertures for accommodating afastener, such as a bolt 264 to secure the clamp 260 to the tube sheet203. The nose 262 operates to apply pressure to the flange 246 andcompress the seal member 248 against the tube sheet 203. The lever 261operates to selectively move the nose 262 toward and away from the tubesheet 203. In other embodiments, the clamps 260 can be hand-tightened,such as using wing nuts.

In typical operation, there is an overall pressure drop across thefilter arrangement 202 of about 0.6–1.6 inches of water. This includesboth the primary filter element 220 and the prefilter 222. Typically,the pressure drop across the prefilter 222 alone will be about 0.2–0.6inches of water, while the pressure drop across the primary element 220alone will be about 0.4–1 inch of water.

Another example of an air filter arrangement 213 usable in the system304 or system 302 is shown in FIGS. 34–36. With the exception ofpreferred media formulations provided in Section H below, the air filterarrangement is described in commonly assigned U.S. patent applicationSer. No. 09/593,257 filed Jun. 13, 2000, incorporated by referenceherein.

FIG. 35 illustrates the filter arrangement 213 in an exploded,unassembled form, while FIG. 14 illustrates the filter arrangement 213assembled for use. In general, the air filter arrangement 213 includes amoisture separator 270, a filter assembly 272, and a filter housing 274.The filter housing 274 is typically secured within a tube sheet 276 whenassembled for use. Preferably, the filter housing 274 is secured withinthe tube sheet 276 by welding the housing 274 to the tube sheet 276 orby bolting the housing 274 to the tube sheet 276.

An access door 278 provides access to the filter arrangement 213 whenassembled and allows air to be drawn into the system 302. In general,the access door 278 is designed and constructed to fit the particularhousing of the system, such as the system 302, of FIG. 33, it is to beinstalled in and to provide access to the filter arrangement 213, whenassembled. The access door 278 is also designed and constructed to allowair to enter the system 210, FIG. 33.

The access door 278 preferably includes an air flow resistancearrangement 280. In general, the air flow resistance arrangement 280directs air flow into the filter arrangement 213 in a particulardirection to reduce resistance through the system 302. The air flowresistance arrangement 280 also aids in noise attenuation. In theembodiment depicted in FIG. 34, the air flow resistance arrangement isdepicted as a plurality of louvers 282. The louvers 282 also aid inprotecting the system 210 from entry of large objects and moisture intothe system 302, FIG. 33. The louvers 282 further aid in noiseattenuation.

Moisture in the incoming air stream can damage the integrity of thefilter assembly 272, and damage, i.e. contribute to rusting, theinternal mechanisms of the system 302. To address this, the filterarrangement includes moisture separator 270. In general, the moistureseparator 270 separates and collects moisture from the incoming airstream prior to reaching the filter assembly 272. In one embodiment, themoisture separator 270 includes a plurality of flat screens, e.g., wiremesh.

In general, the filter assembly 272 removes contaminants from theincoming air stream 212, FIG. 33, prior to entry into the internalmechanisms of the system 302. Preferably, the filter assembly 272 isconfigured to permit straight through flow directly through the filterassembly 272, entering at an inlet face 284 and exiting at an oppositelydisposed outlet face 285, wherein the direction of fluid flow enteringthe inlet face 284 is in the same direction of fluid flow exiting theoutlet face 285.

The filter assembly 272 includes a media pack 286 formed from flutedmedia 288 rolled into a cylinder, as explained above in connection withFIGS. 22 and 23. The media 288 can be a polyester synthetic media, amedia made from cellulose, or blends of these types of materials andtreated with a coating or a layer of fine fiber. Preferred mediaformulations are given in Section H below.

The filter assembly 272 depicted includes a pull mechanism 290. The pullmechanism 290 is constructed to allow a user to easily remove the filterassembly 272 from the filter housing 274. In the one shown, the pullmechanism 290 includes a handle 292 and a retention mechanism 294 (FIG.34). Typically, the handle 292 is a knob 296. In the one shown in FIG.34, the retention mechanism 294 includes a bolt 298 attached to the knob296 and a nut 299 at the other end of the bolt. Alternatively, the pullmechanism and the core of the filter media could be one integrated unit.

In general, the filter housing 274 is constructed to receive and holdthe filter assembly 272 and to facilitate sealing with the filterassembly 272. In the one shown in FIG. 16, the filter housing 274includes a transition area 302 angled from an outer wall 304 at an angleof at least 10 degrees, preferably between 10 and 210 degrees, and mostpreferably about 15 degrees. The transition area 302 aids in sealing thefilter assembly 272 as will be explained in more detail below.

The filter housing 274 further includes a mounting flange 306. Themounting flange 306 secures the filter housing 274 to the tube sheet 276through a fastener arrangement (e.g., bolts). The housing 274 alsoincludes a stopping arrangement 308. The stopping arrangement 308 seatsthe filter assembly 272 within the housing 274 to prevent the filterassembly 272 from being pushed too far into the housing 274. Thestopping arrangement 308 also helps in ensuring a proper seal betweenthe filter assembly 272 and the housing 274.

The stopping arrangement 308 includes a stop 310. Preferably, the stop310 projects from the outer wall 304 a distance sufficient to preventthe filter assembly 272 from bypassing the stop 310. During use, thefilter assembly 272 rests upon a top surface 311 of the stop 310.

The filter assembly 272 also includes a sealing gasket 312. The sealinggasket 312 seals the filter assembly 272 in the filter housing 274,inhibiting air from entering the system 302 between the filter assembly272 and the filter housing 274 and bypassing the filter assembly 272.This ensures that the air stream goes substantially through the filterassembly 272. In the one illustrated, the sealing gasket 312 extendscircumferentially around the radial edge of the filter assembly 272. Inone embodiment, the sealing gasket 312 comprises closed cell foam; ofcourse, the sealing gasket 312 can comprise other suitable material.

During use, the sealing gasket 312 seals a joint 314 between the filterassembly 272 and the filter housing 274. During installation, the filterassembly 272 is inserted into the housing 274 until an end 315 restsagainst the stop 310. As the filter assembly 272 is installed, thesealing gasket 312 is compressed in the transition area 302 between thefilter assembly 272 and the housing 274, sealing the joint 314.

During assembly, the filter housing 274 is slid into the tube sheet 276until the mounting flange 306 of the filter housing 274 is seatedagainst the tube sheet 276. Next, the filter assembly 272 is seatedwithin the filter housing 274. The filter assembly 272 is slid into thefilter housing 274 until the end 315 of the filter assembly 272 restsagainst the stop 310. The sealing gasket 312 is partially compressed andthe filter assembly 272 is snugly held with the filter housing 274.

In operation, the filter arrangement 213 is used as follows: Air to befiltered in the system 302 is directed at arrows 212 into the intakesystem 211. The air flows through the filter assembly 272. The airenters at the inlet face 284, passes through the fluted construction288, and exits through the outlet face 285. From there, the air is takeninto the turbine or generator 215.

G. Typical System; Fuel Cell Air Intake

A fuel cell air intake is shown schematically in FIG. 37 at 330. Asdepicted in FIG. 37, atmospheric or ambient air 331 enters filterassembly 332 via an inlet 333. Prior to entering filter assembly 332,atmospheric air 331 is dirty air having various physical (e.g.,particulate) and chemical contaminants. Filter assembly 332 isconstructed to remove various contaminants from the dirty air to provideclean air 334 that exits from filter assembly 332. Clean air 334 is theintake air for a fuel cell 335, used to generate power.

Referring still to FIG. 37, atmospheric air 331 enters filter assembly332 as dirty air through inlet 333 in housing 336 and progresses todirty air side 337 of filter element 338. As the air passes throughfilter element 338 to clean air side 339, contaminants are removed byfilter element 338 to provide filtered air 334. Filtered air 334 exitsfilter assembly 332 through outlet 340 of housing 336 and is used byequipment 341.

Filter assembly 332 also optionally includes a noise suppression element342 to reduce or suppress the level of noise or sound emanating fromequipment 341. Suppression element 342 may be positioned within housing336, and in some embodiments, suppression element 342 is defined byhousing 336.

Equipment 341 includes a compressor 343 that provides air to fuel cell335 to use in its catalytic reaction. Compressor 343 emits noise,typically in the range of 3 Hertz to 30,000 Hertz, sometimes as high as50,000 Hertz, at a level of 85 to 110 dB at one meter. Suppressionelement 342, reduces the level of sound traveling upstream fromcompressor 343 by at least 3 dB, typically by at least 6 dB, andpreferably by at least 25 dB.

The fuel cell 335 takes in hydrogen fuel 345, emits a by-product ofwater and carbon dioxide 346, and generates power 347. In general, fuelcells are devices consisting of two electrodes (an anode and a cathode)that sandwich an electrolyte. A fuel containing hydrogen flows to theanode, where the hydrogen electrons are freed, leaving positivelycharged ions. The electrons travel through an external circuit in whichthe ions diffuse through the electrolyte. At the cathode, the electronscombine with the hydrogen ions and oxygen to form water and carbondioxide, by-products. A common oxygen source is air. To speed thecathodic reaction, a catalyst is often used. Examples of catalysts oftenused in the fuel cell reaction include nickel, platinum, palladium,cobalt, cesium, neodymium, and other rare earth metals. The reactants inthe fuel cell are the hydrogen fuel and an oxidizer.

Typically, “low temperature fuel cells” operate at temperatures,typically about 70 to 100° C., sometimes as high as 200° C. Hightemperature fuel cells are typically not as sensitive to chemicalcontamination due to their higher operating temperature. Hightemperature fuel cells are, however, sensitive to particulatecontamination, and some forms of chemical contamination, and thus hightemperature fuel cells benefit from the filtering features as describedherein. One type of low temperature fuel cell is commonly referred to asa “PEM”, is named for its use of a proton exchange membrane. Examples ofother various types of fuel cells that can be used in combination withthe filter assembly of the present invention include, for example, U.S.Pat. Nos. 6,110,611; 6,117,579; 6,103,415; and 6,083,637, thedisclosures of which are incorporated here by reference. Various fuelcells are commercially available from, for example, Ballard PowerSystems, Inc. of Vancouver, Canada; International Fuel Cells, ofConnecticut; Proton Energy Systems, Inc. of Rocky Hill, Conn.; AmericanFuel Cell Corp. of Massachusetts; Siemans A G of Erlangen, Germany;Energy Partners, L.C. of Florida; General Motors of Detroit, Mich.; andToyota Motor Corporation of Japan.

The filter assemblies, as described below, remove contaminants from theatmospheric air before the air is used in the fuel cell operation. Asexplained below, constructing the filter assembly in the form of acomposite of a barrier media and at least a single layer, and in someinstances, multiple layers of “fine fiber” can enhance the performance(the operating efficiency, in particular) of the filter assembly. Thefine fiber treatment is advantageous in improving filter efficiency inmost filter geometry and environment. In certain harsh environments witha filter temperature over 120° F., which includes both low temperatureand high temperature fuel cells the fine fiber can often survive andprovide extended lifetime filtration.

H. Example Filter Arrangement for Fuel Cell Air Intake Systems

FIG. 38 illustrates a filter assembly 350 usable in the system of FIG.37. Filter assembly 350 includes a housing 352 which defines an inlet354 and an outlet 356. Dirty air enters filter assembly 350 via inlet354, and clean air exits via outlet 356.

Positioned within housing 352 is a filter element 358 and a noisesuppression element 360. Suppression element 360 comprises a firstresonator 361 and a second resonator 362. First resonator 361 isconfigured to attenuate a peak of about 900 Hz, and second resonator 362is configured to attenuate a peak of about 550 Hz.

Filter element 358 of FIG. 38 is generally constructed analogously asthe filter element construction 40 (FIG. 22). As such, it includes amedia pack 364 of fluted media 366 (as described with respect to FIG. 3)rolled into filter element 358.

When filter element 358 is used with inline-flow housing 352, the airwill enter through inlet 354 of housing 352 in one direction, enterfilter element 358 through first flow face 368 in the same direction,exit filter element 358 in the same direction from second flow face 370,and exit housing 352 through outlet 356 also in the same direction.

As with the embodiment of FIGS. 22 and 24, a radial seal 372 is formedby compression of the sealing gasket 374 between and against a frame 376and an inner sealing surface 378 of the housing.

Filter assembly 350 preferably also includes a portion designed toremove contaminants from the atmosphere by either adsorption orabsorption. As used herein, the terms “adsorb”, “adsorption”,“adsorbent” and the like, are intended to also include the mechanisms ofabsorption and adsorption.

The chemical removal portion typically includes a physisorbent orchemisorbent material, such as, for example, desiccants (i.e., materialsthat adsorb or absorb water or water vapor) or materials that adsorb orabsorb volatile organic compounds and/or acid gases and/or basic gases.The terms “adsorbent material,” “adsorption material,” “adsorptivematerial,” “absorbent material,” “absorption material,” “absorptivematerial,” and any variations thereof, are intended to cover anymaterial that removes chemical contaminants by adsorption or absorption.Suitable adsorbent materials include, for example, activated carbon,activated carbon fibers, impregnated carbon, activated alumina,molecular sieves, ion-exchange resins, ion-exchange fibers, silica gel,alumina, and silica. Any of these materials can be combined with, coatedwith, or impregnated with materials such as potassium permanganate,calcium carbonate, potassium carbonate, sodium carbonate, calciumsulfate, citric acid, or mixtures thereof. In some embodiments, theadsorbent material can be combined or impregnated with a secondmaterial.

The adsorbent material typically includes particulates or granulatedmaterial and can be present as granules, beads, fibers, fine powders,nanostructures, nanotubes, aerogels, or can be present as a coating on abase material such as a ceramic bead, monolithic structures, papermedia, or metallic surface. Typically, the adsorbent materials,especially particulate or granulated materials, are provided as a bed ofmaterial.

Alternately, the adsorbent material can be shaped into a monolithic orunitary form, such as a large tablet, granule, bead, or pleatable orhoneycomb structure that optionally can be further shaped. In at leastsome instances, the shaped adsorbent material substantially retains itsshape during the normal or expected lifetime of the filter assembly. Theshaped adsorbent material can be formed from a free-flowing particulatematerial combined with a solid or liquid binder that is then shaped intoa non-free-flowing article. The shaped adsorbent material can be formedby, for example, a molding, a compression molding, or an extrusionprocess. Shaped adsorbent articles are taught, for example, in U.S. Pat.No. 5,189,092 (Koslow), and U.S. Pat. No. 5,331,037 (Koslow), which areincorporated herein by reference.

The binder used for providing shaped articles can be dry, that is, inpowdered and/or granular form, or the binder can be a liquid, solvated,or dispersed binder. Certain binders, such as moisture curable urethanesand materials typically referred to as “hot melts”, can be applieddirectly to the adsorbent material by a spray process. In someembodiments, a temporary liquid binder, including a solvent ordispersant which can be removed during the molding process, is used.Suitable binders include, for example, latex, microcrystallinecellulose, polyvinyl alcohol, ethylene-vinyl acetate, starch,carboxylmethyl cellulose, polyvinylpyrrolidone, dicalcium phosphatedihydrate, and sodium silicate. Preferably the composition of a shapedmaterial includes at least about 70%, by weight, and typically not morethan about 98%, by weight, adsorbent material. In some instances, theshaped adsorbent includes 85 to 95%, preferably, approximately 90%, byweight, adsorbent material. The shaped adsorbent typically includes notless than about 2%, by weight, binder and not more than about 30%, byweight, binder.

Another embodiment of a suitable adsorbent material for use in thechemical removal portion is an adsorbent material that includes acarrier. For example, a mesh or scrim can be used to hold the adsorbentmaterial and binder. Polyester and other suitable materials can be usedas the mesh or scrim. Typically, any carrier is not more than about 50%of the weight of the adsorbent material, and is more often about 20 to40% of the total adsorbent weight. The amount of binder in the shapedadsorbed article with the carrier typically ranges about 10 to 50% ofthe total adsorbent weight and the amount of adsorbent materialtypically ranges about 20 to 60% of the total adsorbent weight.

The chemical removal portion can include strongly basic materials forthe removal of acid contaminants from the air, or strongly acidicmaterials for the removal of basic contaminants from the air, or both.Preferably, the basic materials and acidic materials are removed fromeach other so that they do not cancel each other. In some embodiments,the adsorbent material itself may be the strongly acidic or strong basicmaterial. Examples of such materials include materials such as polymerparticulates, activated carbon media, zeolites, clays, silica gels, andmetal oxides. In other embodiments, the strongly acidic materials andthe strongly basic materials can be provided as surface coatings oncarriers such as granular particulate, beads, fibers, fine powders,nanotubes, and aerogels. Alternately or additionally, the acidic andbasic material that forms the acidic and basic surfaces may be presentthroughout at least a portion of the carrier; this can be done, forexample, by coating or impregnating the carrier material with the acidicor basic material.

Both basic and acidic materials may be present in the chemical removalportion of the filter element; however, it is preferable that the twotypes of materials are spaced from each other so that they do not reactwith and neutralize one another. In some embodiments, the basicmaterial, acidic material, or both, may be spaced from an adsorbentmaterial, such as activated carbon.

Examples of acidic compounds that are often present in atmospheric airand are considered as contaminants for fuel cells include sulfur oxides,nitrogen oxides, hydrogen sulfide, hydrogen chloride, and volatileorganic acids and nonvolatile organic acids. Examples of basic compoundsthat are often present in atmospheric air and are considered ascontaminants for fuel cells include ammonia, amines, amides, sodiumhydroxides, lithium hydroxides, potassium hydroxides, volatile organicbases and nonvolatile organic bases.

For PEM fuel cells, the cathodic reaction occurs under acidicconditions, thus, it is undesirable to have basic contaminants present.An example of a preferred material for removing basic contaminants, suchas ammonia, is a bed of activated carbon granules impregnated withcitric acid.

A second example of a filter assembly usable in the system of FIG. 37 isshown in fragmented cross-section in FIG. 39 as a filter assembly 380.Filter assembly 380 includes a housing 382 which defines an inlet 384and an outlet 386. Dirty air enters filter assembly 380 via inlet 384,and clean air exits via outlet 386. Sound suppression element 388comprises a resonator 390. A filter element 391 is mounted within thehousing 382 and is analogous to filter element 358.

Filter assembly 380 also includes an adsorbent element 392. Adsorbentelement 392 comprises a cylindrical mass of carbon 393 between ends394,395. In the one depicted, mass of carbon 393 is a hollow, circularextension 397 of activated carbon held together by a thermoplasticbinder. Carbon 393 can be produced, for example, by the teachings ofU.S. Pat. No. 5,189,092 (Koslow), and U.S. Pat. No. 5,331,037 (Koslow).Positioned at first end 394 is a sealing system 396 and positioned atsecond end 395 is a cap 398.

Sealing system 396 provides an air-tight seal between adsorbent element392 and baffle 401. Sealing system 396 is designed to seal adsorbentelement 392 against baffle 401, and, under normal conditions, inhibitair from passing through a region between adsorbent element 392 and thesidewall of housing 382. Sealing system 396 inhibits air flow fromavoiding passing through carbon 393 of adsorbent element 392. Sealingsystem 396 is typically made from a flexible, compressible material,such as polyurethane.

Cap 398 diverts air exiting filter element 358 so that it entersadsorbent element 392 through carbon 393 rather than passing axiallythrough the cylindrical extension of carbon 393. Air from filter element391 impinges on an exposed surface 402 of cap 398 and is rerouted fromits “straight-line” flow to a flow having a radial component. Cap 398includes apertures 404 therein for passage of air through cap 398 sothat the air can reach carbon 393. In addition to managing air flow, cap398 provides anchoring of absorbent element 392 to filter element 391.

Adsorbent element 392 functions both as a chemical removal portion andas an element of sound suppression element 388. Other arrangements ofadsorbent elements and adsorbent materials may also have both a chemicalremoval quality and a sound suppression quality.

I. Preferred Media Construction for Filter Elements Disclosed Above

A fine fiber filter structure includes a bi-layer or multi-layerstructure wherein the filter contains one or more fine fiber layerscombined with or separated by one or more synthetic, cellulosic orblended webs. Another preferred motif is a structure including finefiber in a matrix or blend of other fibers.

We believe important characteristics of the fiber and microfiber layersin the filter structure relate to temperature resistance, humidity ormoisture resistance and solvent resistance, particularly when themicrofiber is contacted with humidity, moisture or a solvent at elevatedtemperatures. Further, a second important property of the materials ofthe invention relates to the adhesion of the material to a substratestructure. The microfiber layer adhesion is an important characteristicof the filter material such that the material can be manufacturedwithout delaminating the microfiber layer from the substrate, themicrofiber layer plus substrate can be processed into a filter structureincluding pleats, rolled materials and other structures withoutsignificant delamination. We have found that the heating step of themanufacturing process wherein the temperature is raised to a temperatureat or near but just below melt temperature of one polymer material,typically lower than the lowest melt temperature substantially improvesthe adhesion of the fibers to each other and the substrate. At or abovethe melt temperature, the fine fiber can lose its fibrous structure. Itis also critical to control heating rate. If the fiber is exposed to itscrystallization temperature for extended period of time, it is alsopossible to lose fibrous structure. Careful heat treatment also improvedpolymer properties that result from the formation of the exterioradditive layers as additive materials migrate to the surface and exposehydrophobic or oleophobic groups on the fiber surface.

The criteria for performance is that the material be capable ofsurviving intact various operating temperatures, i.e. a temperature of140° F., 160° F., 270° F., 300° F. for a period of time of 1 hour or 3hours, depending on end use, while retaining 30%, 50%, 80% or 90% offilter efficiency. An alternative criteria for performances that thematerial is capable of surviving intact at various operatingtemperatures, i.e. temperatures of 140° F., 160° F., 270° F., 300° F.,for a period of time of 1 hours or 3 hours depending on end use, whileretaining, depending on end use, 30%, 50%, 80% or 90% of effective finefibers in a filter layer. Survival at these temperatures is important atlow humidity, high humidity, and in water saturated air. The microfiberand filter material of the invention are deemed moisture resistant wherethe material can survive immersion at a temperature of greater than 160°F. while maintaining efficiency for a time greater than about 5 minutes.Similarly, solvent resistance in the microfiber material and the filtermaterial of the invention is obtained from a material that can survivecontact with a solvent such as ethanol, a hydrocarbon, a hydraulicfluid, or an aromatic solvent for a period of time greater than about 5minutes at 70° F. while maintaining 50% efficiency.

The fine fiber materials of the invention can be used in a variety offilter applications including pulse clean and non-pulse cleaned filtersfor dust collection, gas turbines and engine air intake or inductionsystems; gas turbine intake or induction systems, heavy duty engineintake or induction systems, light vehicle engine intake or inductionsystems; vehicle cabin air; off road vehicle cabin air, disk drive air,photocopier-toner removal; HVAC filters in both commercial orresidential filtration applications. Paper filter elements are widelyused forms of surface loading media. In general, paper elements comprisedense mats of cellulose, synthetic or other fibers oriented across a gasstream carrying particulate material. The paper is generally constructedto be permeable to the gas flow, and to also have a sufficiently finepore size and appropriate porosity to inhibit the passage of particlesgreater than a selected size therethrough. As the gases (fluids) passthrough the filter paper, the upstream side of the filter paper operatesthrough diffusion and interception to capture and retain selected sizedparticles from the gas (fluid) stream. The particles are collected as adust cake on the upstream side of the filter paper. In time, the dustcake also begins to operate as a filter, increasing efficiency. This issometimes referred to as “seasoning,” i.e. development of an efficiencygreater than initial efficiency.

A simple filter design such as that described above is subject to atleast two types of problems. First, a relatively simple flaw, i.e.rupture of the paper, results in failure of the system. Secondly,particulate material rapidly builds up on the upstream side of thefilter, as a thin dust cake or layer, increasing the pressure drop.Various methods have been applied to increase the “lifetime” ofsurface-loaded filter systems, such as paper filters. One method is toprovide the media in a pleated construction, so that the surface area ofmedia encountered by the gas flow stream is increased relative to aflat, non-pleated construction. While this increases filter lifetime, itis still substantially limited. For this reason, surface loaded mediahas primarily found use in applications wherein relatively lowvelocities through the filter media are involved, generally not higherthan about 20–30 feet per minute and typically on the order of about 10feet per minute or less. The term “velocity” in this context is theaverage velocity through the media (i.e. flow volume per media area).

In general, as air flow velocity is increased through a pleated papermedia, filter life is decreased by a factor proportional to the squareof the velocity. Thus, when a pleated paper, surface loaded, filtersystem is used as a particulate filter for a system that requiressubstantial flows of air, a relatively large surface area for the filtermedia is needed. For example, a typical cylindrical pleated paper filterelement of an over-the-highway diesel truck will be about 9–15 inches indiameter and about 12–24 inches long, with pleats about 1–2 inches deep.Thus, the filtering surface area of media (one side) is typically 30 to300 square feet.

In many applications, especially those involving relatively high flowrates, an alternative type of filter media, sometimes generally referredto as “depth” media, is used. A typical depth media comprises arelatively thick tangle of fibrous material. Depth media is generallydefined in terms of its porosity, density or percent solids content. Forexample, a 2–3% solidity media would be a depth media mat of fibersarranged such that approximately 2–3% of the overall volume comprisesfibrous materials (solids), the remainder being air or gas space.

Another useful parameter for defining depth media is fiber diameter. Ifpercent solidity is held constant, but fiber diameter (size) is reduced,pore size or interfiber space is reduced; i.e. the filter becomes moreefficient and will more effectively trap smaller particles.

A typical conventional depth media filter is a deep, relatively constant(or uniform) density, media, i.e. a system in which the solidity of thedepth media remains substantially constant throughout its thickness. By“substantially constant” in this context, it is meant that onlyrelatively minor fluctuations in density, if any, are found throughoutthe depth of the media Such fluctuations, for example, may result from aslight compression of an outer engaged surface, by a container in whichthe filter media is positioned.

Gradient density depth media arrangements have been developed. some sucharrangements are described, for example, in U.S. Pat. Nos. 4,082,476;5,238,474; and 5,364,456. In general, a depth media arrangement can bedesigned to provide “loading” of particulate materials substantiallythroughout its volume or depth. Thus, such arrangements can be designedto load with a higher amount of particulate material, relative tosurface loaded systems, when full filter lifetime is reached. However,in general the tradeoff for such arrangements has been efficiency,since, for substantial loading, a relatively low solidity media isdesired. Gradient density systems such as those in the patents referredto above, have been designed to provide for substantial efficiency andlonger life. In some instances, surface loading media is utilized as a“polish” filter in such arrangements.

A filter media construction according to the present invention includesa first layer of permeable coarse fibrous media or substrate having afirst surface. A first layer of fine fiber media is secured to the firstsurface of the first layer of permeable coarse fibrous media. Preferablythe first layer of permeable coarse fibrous material comprises fibershaving an average diameter of at least 10 microns, typically andpreferably about 12 (or 14) to 30 microns. Also preferably the firstlayer of permeable coarse fibrous material comprises a media having abasis weight of no greater than about 200 grams/meter², preferably about0.50 to 150 g/m², and most preferably at least 8 g/m². Preferably thefirst layer of permeable coarse fibrous media is at least 0.0005 inch(12 microns) thick, and typically 0.0006 to 0.02 (15 to 500 microns)thick and preferably is about 0.001 to 0.030 inch (25–800 microns)thick.

In preferred arrangements, the first layer of permeable coarse fibrousmaterial comprises a material which, if evaluated separately from aremainder of the construction by the Frazier permeability test, wouldexhibit a permeability of at least 1 meter(s)/min, and typically andpreferably about 2–900 meters/min. Herein when reference is made toefficiency, unless otherwise specified, reference is meant to efficiencywhen measured according to ASTM-1215-89, with 0.78μ monodispersepolystyrene spherical particles, at 20 fpm (6.1 meters/min) as describedherein.

Preferably the layer of fine fiber material secured to the first surfaceof the layer of permeable coarse fibrous media is a layer of nano- andmicrofiber media wherein the fibers have average fiber diameters of nogreater than about 2 microns, generally and preferably no greater thanabout 1 micron, and typically and preferably have fiber diameterssmaller than 0.5 micron and within the range of about 0.05 to 0.5micron. Also, preferably the first layer of fine fiber material securedto the first surface of the first layer of permeable coarse fibrousmaterial has an overall thickness that is no greater than about 30microns, more preferably no more than 20 microns, most preferably nogreater than about 10 microns, and typically and preferably that iswithin a thickness of about 1–8 times (and more preferably no more than5 times) the fine fiber average diameter of the layer.

Certain preferred arrangements according to the present inventioninclude filter media as generally defined, in an overall filterconstruction. Some preferred arrangements for such use comprise themedia arranged in a cylindrical, pleated configuration with the pleatsextending generally longitudinally, i.e. in the same direction as alongitudinal axis of the cylindrical pattern. For such arrangements, themedia may be imbedded in end caps, as with conventional filters. Sucharrangements may include upstream liners and downstream liners ifdesired, for typical conventional purposes.

In some applications, media according to the present invention may beused in conjunction with other types of media, for example conventionalmedia, to improve overall filtering performance or lifetime. Forexample, media according to the present invention may be laminated toconventional media, be utilized in stack arrangements; or beincorporated (an integral feature) into media structures including oneor more regions of conventional media. It may be used upstream of suchmedia, for good load; and/or, it may be used downstream fromconventional media, as a high efficiency polishing filter.

Certain arrangements according to the present invention may also beutilized in liquid filter systems, i.e. wherein the particulate materialto be filtered is carried in a liquid. Also, certain arrangementsaccording to the present invention may be used in mist collectors, forexample arrangements for filtering fine mists from air.

According to the present invention, methods are provided for filtering.The methods generally involve utilization of media as described toadvantage, for filtering. As will be seen from the descriptions andexamples below, media according to the present invention can bespecifically configured and constructed to provide relatively long lifein relatively efficient systems, to advantage.

Various filter designs are shown in patents disclosing and claimingvarious aspects of filter structure and structures used with the filtermaterials. Engel et al., U.S. Pat. No. 4,720,292, disclose a radial sealdesign for a filter assembly having a generally cylindrical filterelement design, the filter element being sealed by a relatively soft,rubber-like end cap having a cylindrical, radially inwardly facingsurface. Kahlbaugh et al., U.S. Pat. No. 5,082,476, disclose a filterdesign using a depth media comprising a foam substrate with pleatedcomponents combined with the microfiber materials of the invention.Stifelman et al., U.S. Pat. No. 5,104,537, relate to a filter structureuseful for filtering liquid media. Liquid is entrained into the filterhousing, passes through the exterior of the filter into an interiorannular core and then returns to active use in the structure. Suchfilters are highly useful for filtering hydraulic fluids. Engel et al.,U.S. Pat. No. 5,613,992, show a typical diesel engine air intake filterstructure. The structure obtains air from the external aspect of thehousing that may or may not contain entrained moisture. The air passesthrough the filter while the moisture can pass to the bottom of thehousing and can drain from the housing. Gillingham et al., U.S. Pat. No.5,820,646, disclose a Z filter structure that uses a specific pleatedfilter design involving plugged passages that require a fluid stream topass through at least one layer of filter media in a “Z” shaped path toobtain proper filtering performance. The filter media formed into thepleated Z shaped format can contain the fine fiber media of theinvention. Glen et al., U.S. Pat. No. 5,853,442, disclose a bag housestructure having filter elements that can contain the fine fiberstructures of the invention. Berkhoel et al., U.S. Pat. No. 5,954,849,show a dust collector structure useful in processing typically airhaving large dust loads to filter dust from an air stream afterprocessing a workpiece generates a significant dust load in anenvironmental air. Lastly, Gillingham, U.S. Design Pat. No. 425,189,discloses a panel filter using the Z filter design.

The following materials were produced using the following electrospinprocess conditions.

The following materials were spun using either a rotating emitter systemor a capillary needle system. Both were found to produce substantiallythe same fibrous materials.

Using the device generally a fiber is made. The flow rate was 1.5mil/min per emitter, a target distance of 8 inches, an emitter voltageof 88 kV, a relative humidity of 45%, and for the rotating emitter anrpm of 35.

EXAMPLE 1 Effect of Fiber Size

Fine fiber samples were prepared from a copolymer of nylon 6, 66, 610nylon copolymer resin (SVP-651) was analyzed for molecular weight by theend group titration. (J. E. Walz and G. B. Taylor, determination of themolecular weight of nylon, Anal. Chem. Vol. 19, Number 7, pp 448–450(1947). Number average molecular weight was between 21,500 and 24,800.The composition was estimated by the phase diagram of melt temperatureof three component nylon, nylon 6 about 45%, nylon 66 about 20% andnylon 610 about 25%. (Page 286, Nylon Plastics Handbook, Melvin Kohaned. Hanser Publisher, New York (1995)). Reported physical properties ofSVP 651 resin are:

Property ASTM Method Units Typical Value Specific Gravity D-792 — 1.08Water Absorption D-570 % 2.5 (24 hr immersion) Hardness D-240 Shore D 65Melting Point DSC ° C.(° F.) 154 (309) Tensile Strength D-638 MPa (kpsi) 50 (7.3) @ Yield Elongation at Break D-638 % 350 Flexural Modulus D-790MPa (kpsi) 180 (26)  Volume Resistivity D-257 ohm-cm  10¹²to produce fiber of 0.23 and 0.45 micron in diameter. Samples weresoaked in room temperature water, air-dried and its efficiency wasmeasured. Bigger fiber takes longer time to degrade and the level ofdegradation was less as can be seen in the plot of FIG. 12. Whilewishing not to be limited by certain theory, it appears that smallerfibers with a higher surface/volume ratio are more susceptible todegradation due to environmental effects. However, bigger fibers do notmake as efficient filter medium.

EXAMPLE 2 Cross-Linking of Nylon Fibers with Phenolic Resin and EpoxyResin

In order to improve chemical resistance of fibers, chemicalcross-linking of nylon fibers was attempted. Copolyamide (nylon 6, 66,610) described earlier is mixed with phenolic resin, identified asGeorgia Pacific 5137 and spun into fiber. Nylon:Phenolic Resin ratio andits melt temperature of blends are shown here;

Melting Temperature Composition (F. °) Polyamide:Phenolic = 100:0 150Polyamide:Phenolic = 80:20 110 Polyamide:Phenolic = 65:35 94Polyamide:Phenolic = 50:50 65

We were able to produce comparable fiber from the blends. The 50:50blend could not be cross-linked via heat as the fibrous structure wasdestroyed. Heating 65:35 blend below 90 degree C. for 12 hours improvesthe chemical resistance of the resultant fibers to resist dissolution inalcohol. Blends of polyamide with epoxy resin, such Epon 828 from Shelland Epi-Rez 510 can be used.

EXAMPLE 3 Surface Modification Though Fluoro Additive (Scotchgard®)Repellant

Alcohol miscible Scotchgard® FC-430 and 431 from 3M Company were addedto polyamide before spinning. Add-on amount was 10% of solids. Additionof Scotchgard did not hinder fiber formation. THC bench shows thatScotchgard-like high molecular weight repellant finish did not improvewater resistance. Scotchgard added samples were heated at 300° F. for 10minutes as suggested by manufacturer.

EXAMPLE 4 Modification with Coupling Agents

Polymeric films were cast from polyamides with tinanate coupling agentsfrom Kenrich Petrochemicals, Inc. They include isopropyl triisostearoyltitanate (KR TTS), neopentyl (diallyl) oxytri (dioctyl) phosphatotitanate (LICA12), neopentyl (dially) oxy, tri (N-ethylene diamino)ethyl zirconate (NZ44). Cast films were soaked in boiling water. Controlsample without coupling agent loses its strength immediately, whilecoupling agent added samples maintained its form for up to ten minutes.These coupling agents added samples were spun into fiber (0.2 micronfiber).

EXAMPLE 5 Modification with Low Molecular Weight p-tert-butyl phenolPolymer

Oligomers of para-tert-butyl phenol, molecular weight range 400 to 1100,was purchased from Enzymol International, Columbus, Ohio. These lowmolecular weight polymers are soluble in low alcohols, such as ethanol,isopropanol and butanol. These polymers were added to co-polyamidedescribed earlier and electrospun into 0.2 micron fibers without adverseconsequences. Some polymers and additives hinder the electrospinningprocess. Unlike the conventional phenolic resin described in Example 2,we have found that this group of polymers does not interfere with fiberforming process.

We have found that this group of additive protects fine fibers from wetenvironment as see in the plot. FIGS. 13–16 show that oligomers providea very good protection at 140° F., 100% humidity and the performance isnot very good at 160° F. We have added this additive between 5% and 15%of polymer used. We have found that they are equally effectiveprotecting fibers from exposure to high humidity at 140° F. We have alsofound out that performance is enhanced when the fibers are subjected to150° C. for short period of time.

The table 1 shows the effect of temperature and time exposure of 10%add-on to polyamide fibers.

TABLE 1 Efficiency Retained (%) After 140 deg. F. Soak: Heating Time 1min 3 min 10 min Temperature 150 C. ° 98.9 98.8 98.5 98.8 98.9 98.8 130C. ° 95.4 98.7 99.8 96.7 98.6 99.6 110 C. ° 82.8 90.5 91.7 86.2 90.985.7

This was a surprising result. We saw dramatic improvement in waterresistance with this family of additives. In order to understand howthis group of additive works, we have analyzed the fine fiber mat withsurface analysis techniques called ESCA. 10% add-on samples shown inTable 1 were analyzed with ESCA at the University of Minnesota with theresults shown in Table 2.

TABLE 2 Surface Composition (Polymer:Additive Ratio) Heating Time 1 min3 min 10 min Temperature 150 C. °. 40:60 40:60 50:50 130 C. °. 60:4056:44 62:82 110 C. °. 63:37 64:36 59:41 No Heat 77:23

Initially, it did not seem to make sense to find surface concentrationof additive more than twice of bulk concentration. However, we believethat this can be explained by the molecular weight of the additives.Molecular weight of the additive of about 600 is much smaller than thatof host fiber forming polymer. As they are smaller in size, they canmove along evaporating solvent molecules. Thus, we achieve highersurface concentration of additives. Further treatment increases thesurface concentration of the protective additive. However, at 10 minexposure, 150° C., did not increase concentration. This may be anindication that mixing of two components of copolyamide and oligomermolecules is happening as long chain polymer has a time to move around.What this analysis has taught us is that proper selection of posttreatment time and temperature can enhance performance, while too longexposure could have a negative influence.

We further examined the surface of these additive laden microfibersusing techniques called Time of Flight SIMS. This technique involvesbombarding the subject with electrons and observes what is coming fromthe surface. The samples without additives show organic nitrogen speciesare coming off upon bombardment with electron. This is an indicationthat polyamide species are broken off. It also shows presence of smallquantity of impurities, such as sodium and silicone. Samples withadditive without heat treatment (23% additive concentration on surface)show a dominant species of t-butyl fragment, and small but unambiguouspeaks observed peaks observed for the polyamides. Also observed are highmass peaks with mass differences of 148 amu, corresponding to t-butylphenol. For the sample treated at 10 min at 150° C. (50% surfaceadditive concentration by ESCA analysis), inspection shows dominance oft-butyl fragments and trace, if at all, of peaks for polyamide. It doesnot show peaks associated with whole t-butyl phenol and its polymers. Italso shows a peak associated with C₂H₃O fragments.

The ToF SIMS analysis shows us that bare polyamide fibers will give offbroken nitrogen fragment from exposed polymer chain and contaminants onthe surface with ion bombardment. Additive without heat treatment showsincomplete coverage, indicating that additives do not cover portions ofsurface. The t-butyl oligomers are loosely organized on the surface.When ion beam hits the surface, whole molecules can come off along withlabile t-butyl fragment. Additive with heat treatment promotes completecoverage on the surface. In addition, the molecules are tightly arrangedso that only labile fragments such as t-butyl-, and possibly CH═CH—OH,are coming off and the whole molecules of t-butyl phenol are not comingoff. ESCA and ToF SIMS look at different depths of surface. ESCA looksat deeper surface up to 100 Angstrom while ToF SIMS only looks at10-Angstrom depth. These analyses agree.

EXAMPLE 6 Development of Surface Coated Interpolymer

Type 8 Nylon was originally developed to prepare soluble andcrosslinkable resin for coating and adhesive application. This type ofpolymer is made by the reaction of polyamide 66 with formaldehyde andalcohol in the presence of acid. (Ref. Cairns, T. L.; Foster, H. D.;Larcher, A. W.; Schneider, A. K.; Schreiber, R. S. J. Am. Chem. Soc.1949, 71, 651). This type of polymer can be electrospun and can becross-linked. However, formation of fiber from this polymer is inferiorto copolyamides and crosslinking can be tricky.

In order to prepare type 8 nylon, 10-gallon high-pressure reactor wascharged with the following ratio:

Nylon 66 (duPont Zytel 101) 10 pounds Methanol 15.1 pounds Water 2.0pounds Formaldehyde 12.0 pounds

The reactor is then flushed with nitrogen and is heated to at least 135°C. under pressure. When the desired temperature was reached, smallquantity of acid was added as catalyst. Acidic catalysts includetrifluoroacetic acid, formic acid, toluene sulfonic acid, maleic acid,maleic anhydride, phthalic acid, phthalic anhydride, phosphoric acid,citric acid and mixtures thereof. Nafion® polymer can also be used as acatalyst. After addition of catalyst, reaction proceeds up to 30minutes. Viscous homogeneous polymer solution is formed at this stage.After the specified reaction time, the content of the high pressurevessel is transferred to a bath containing methanol, water and base,like ammonium hydroxide or sodium hydroxide to shortstop the reaction.After the solution is sufficiently quenched, the solution isprecipitated in deionized water. Fluffy granules of polymer are formed.Polymer granules are then centrifuged and vacuum dried. This polymer issoluble in, methanol, ethanol, propanol, butanol and their mixtures withwater of varying proportion. They are also soluble in blends ofdifferent alcohols.

Thus formed alkoxy alkyl modified type 8 polyamide is dissolved inethanol/water mixture. Polymer solution is electrospun in a mannerdescribed in Barris U.S. Pat. No. 4,650,516. Polymer solution viscositytends to increase with time. It is generally known that polymerviscosity has a great influence in determining fiber sizes. Thus, it isdifficult to control the process in commercial scale, continuousproduction. Furthermore, under same conditions, type 8 polyamides do notform microfibers as efficiently as copolyamides. However, when thesolution is prepared with addition of acidic catalyst, such as toluenesulfonic acid, maleic anhydride, trifluoro methane sulfonic acid, citricacid, ascorbic acid and the like, and fiber mats are carefullyheat-treated after fiber formation, the resultant fiber has a very goodchemical resistance. (FIG. 13). Care must be taken during thecrosslinking stage, so that one does not destroy fibrous structure.

We have found a surprising result when type 8 polyamide (polymer B) isblended with alcohol soluble copolyamides. By replacing 30% by weight ofalkoxy alkyl modified polyamide 66 with alcohol soluble copolyamide likeSVP 637 or 651 (polymer A), Elvamide 8061, synergistic effects werefound. Fiber formation of the blend is more efficient than either of thecomponents alone. Soaking in ethanol and measuring filtration efficiencyshows better than 98% filtration efficiency retention, THC bench testingshowing comparable results with Type 8 polyamide alone. This type blendshows that we can obtain advantage of efficient fiber formation andexcellent filtration characteristic of copolyamide with advantage ofexcellent chemical resistance of crosslinked type 8 polyamide. Alcoholsoak test strongly suggests that non-crosslinkable copolyamide hasparticipated in crosslinking to maintain 98% of filtration efficiency.

DSC (see FIGS. 17–20) of blends of polymer A and B becomeindistinguishable from that of polymer A alone after they are heated to250° C. (fully crosslinked) with no distinct melt temperature. Thisstrongly suggests that blends of polymer A and B are a fully integratedpolymer by polymer B crosslinking with polymer A. This is a completelynew class of polyamide.

Similarly, melt-blend poly (ethylene terephthalate) with poly(butyleneterephthalate) can have similar properties. During the melt processingat temperatures higher than melt temperature of either component, estergroup exchange occurs and inter polymer of PET and PBT formed.Furthermore, our crosslinking temperature is lower than either of singlecomponent. One would not have expected that such group exchange occur atthis low temperature. Therefore, we believe that we found a new familyof polyamide through solution blending of Type A and Type B polyamideand crosslinking at temperature lower than the melting point of eithercomponent.

When we added 10% by weight of t-butyl phenol oligomer (Additive 7) andheat treated at temperature necessary for crosslinking temperature, wehave found even better results. We theorized that hydroxyl functionalgroup of t-butyl phenol oligomers would participate in reaction withfunctional group of type 8 nylons. What we have found is this componentsystem provides good fiber formation, improved resistance to hightemperature and high humidity and hydrophobicity to the surface of finefiber layers.

We have prepared samples of mixture of Polymer A and Polymer B (Sample6A) and another sample of mixture of Polymer A, Polymer B and Additive &(Sample 6B). We then formed fiber by electrospinning process, exposedthe fiber mat at 300° F. for 10 minutes and evaluated the surfacecomposition by ESCA surface analysis.

Table shows ESCA analysis of Samples 6A and 6B.

Composition (%) Sample 6A Sample 6B Polymer A 30 30 Polymer B 70 70Additive 7 0 10 Surface Composition W/O Heat W/Heat W/O Heat W/HeatPolymer A&B (%) 100 100 68.9 43.0 Additive 7 0 0 31.1 57.0

ESCA provides information regarding surface composition, except theconcentration of hydrogen. It provides information on carbon, nitrogenand oxygen. Since the Additive 7 does not contain nitrogen, we canestimate the ratio of nitrogen containing polyamides and additive thatdoes not contain nitrogen by comparing concentration of nitrogen.Additional qualitative information is available by examining O 1sspectrum of binding energy between 535 and 527 eV. C═O bond has abinding energy at around 531 eV and C—O bond has a binding energy at 533eV. By comparing peak heights at these two peaks, one can estimaterelative concentration of polyamide with predominant C═O and additivewith solely C—O groups. Polymer B has C—O linkage due to modificationand upon crosslinking the concentration of C—O will decrease. ESCAconfirms such reaction had indeed occurred, showing relative decrease ofC—O linkage. (FIG. 4 for non heat treated mixture fiber of Polymer A andPolymer B, FIG. 5 for heat treated mixture fiber of Polymer A andPolymer B). When Additive 7 molecules are present on the surface, onecan expect more of C—O linkage. This is indeed the case as can be seenin FIGS. 6 and 7. (FIG. 6 for as-spun mixture fibers of Polymer A,Polymer B and Additive 7. FIG. 7 for heat treated mixture fibers ofPolymer A, Polymer B and Additive 7). FIG. 6 shows that theconcentration of C—O linkage increases for Example 7. The finding isconsistent with the surface concentration based on XPS multiplexspectrum of FIGS. 8 through 11.

The t-butyl oligomer molecules migrate toward the surface of the finefibers and form hydrophobic coating of about 50 Å. Type 8 nylon hasfunctional groups such as —CH₂OH and —CH₂OCH₃, which we expected toreact with —OH group of t-butyl phenol. Thus, we expected to see lessoligomer molecules on the surface of the fibers. We have found that ourhypothesis was not correct and we found the surface of the interpolymerhas a thin coating.

Samples 6A, 6B and a repeat of sample described in Section 5 have beenexposed THC bench at 160° F. at 100% RH. In previous section, thesamples were exposed to 140° F. and 100% RH. Under these conditions,t-butyl phenol protected terpolymer copolyamide from degradation.However, if the temperature is raised to 160° F. and 100% RH, then thet-butyl phenol oligomer is not as good in protecting the underlyingterpolymer copolyamide fibers. We have compared samples at 160° F. and100% RH.

TABLE Retained Fine Fiber Efficiency after Exposure to 160° F. and 100%RH Sample After 1 Hr. After 2 Hrs. After 3 Hrs. Sample 6A 82.6 82.6 85.9Sample 6B 82.4 88.4 91.6 Sample 5 10.1The table shows that Sample 6B helps protect exposure to hightemperature and high humidity.

More striking difference shows when we exposed to droplets of water on afiber mat. When we place a drop of DI water in the surface of Sample 6A,the water drops immediately spread across the fiber mat and they wet thesubstrate paper as well. On the other hand, when we place a drop ofwater on the surface of Sample 6B, the water drop forms a bead and didnot spread on the surface of the mat. We have modified the surface ofSample 16 to be hydrophobic by addition of oligomers of p-t-butylphenol. This type of product can be used as a water mist eliminator, aswater drops will not go through the fine fiber surface layer of Sample6B.

Samples 6A, 6B and a repeat sample of Section 5 were placed in an ovenwhere the temperature was set at 310° F. Table shows that both Samples6A and 6B remain intact while Sample of Section 5 was severely damaged.

TABLE Retained Fine Fiber Efficiency after Exposure to 310° F. SampleAfter 6 Hrs. After 77 Hrs. Sample 6A 100% 100% Sample 6B 100% 100%Sample 5  34%  33%

While addition of oligomer to Polymer A alone improved the hightemperature resistance of fine fiber layer, the addition of Additive 7has a neutral effect on the high temperature exposure.

We have clearly shown that the mixture of terpolymer copolyamide, alkoxyalkyl modified nylon 66 and oligomers of t-butyl phenol provides asuperior products in helping fine fibers under severe environment withimproved productivity in manufacturing over either mixture of terpolymercopolyamide and t-butyl phenol oligomer or the mixture of terpolymercopolyamide and alkoxy alkyl modified nylon 66. These two componentsmixture are also improvement over single component system.

EXAMPLE 7 Compatible Blend of Polyamides and Bisphenol A Polymers

A new family of polymers can be prepared by oxidative coupling ofphenolic ring (Pecora, A; Cyrus, W. U.S. Pat. No. 4,900,671 (1990) andPecora, A; Cyrus, W.; Johnson, M. U.S. Pat. No. 5,153,298 (1992)). Ofparticular interest is polymer made of Bisphenol A sold by Enzymol Corp.Soybean Peroxidase catalyzed oxidation of Bisphenol A can start fromeither side of two —OH groups in Bisphenol A. Unlike Bisphenol A basedpolycarbonate, which is linear, this type of Bisphenol A polymer formshyperbranched polymers. Because of hyperbranched nature of this polymer,they can lower viscosity of polymer blend.

We have found that this type of Bisphenol A polymer can be solutionblended with polyamides. Reported Hansen's solubility parameter fornylon is 18.6. (Page 317, Handbook of Solubility Parameters and othercohesion parameters, A. Barton ed., CRC Press, Boca Raton Fla., 1985) Ifone calculates solubility parameter (page 61, Handbook of SolubilityParameters), then the calculated solubility parameter is 28.0. Due tothe differences in solubility parameter, one would not expect that theywould be miscible with each other. However, we found that they are quitemiscible and provide unexpected properties.

50:50 blend of Bisphenol A resin of M.W. 3,000 and copolyamide was madein ethanol solution. Total concentration in solution was 10%.Copolyamide alone would have resulted in 0.2 micron fiber diameter.Blend resulted in lofty layer of fibers around 1 micron. Bisphenol A of7,000 M.W. is not stable with copolyamide and tends to precipitate.

DSC of 50:50 blend shows lack of melting temperature. Copolyamide hasmelting temperature around 150 degree C. and Bisphenol A resin is aglassy polymer with Tg of about 100. The blend shows lack of distinctmelting. When the fiber mat is exposed to 100 degree C., the fiber matdisappears. This blend would make an excellent filter media where upperuse temperature is not very high, but low-pressure drop is required.This polymer system could not be crosslinked with a reasonable manner.

EXAMPLE 8 Dual Roles of Bisphenol A Polymer as Solvent and Solid inBlend

A surprising feature of Bisphenol A polymer blend is that in solutionform Bisphenol A polymer acts like a solvent and in solid form thepolymer acts as a solid. We find dual role of Bisphenol A polymer trulyunique.

The following formulation is made:

Alkoxy alkyl modified PA 66: Polymer B 180 g Bisphenol A Resin (3,000MW): Polymer C 108 g Ethanol 190 Grade 827 g Acetone 218 8 DI water 167g Catalyst 9.3 g

The viscosity of this blend was 32.6 centipoise by Brookfieldviscometer. Total polymer concentration was be 19.2%. Viscosity ofPolymer B at 19.2% is over 200 centipoise. Viscosity of 12% polymer Balone in similar solvent is around 60 centipoise. This is a clearexample that Bisphenol A resin acts like a solvent because the viscosityof the total solution was lower than expected. Resultant fiber diameterwas 0.157 micron. If polymer B alone participated in fiber formation,the expected fiber size would be less than 0.1 micron. In other words,Polymer C participated in fiber formation. We do not know of any othercase of such dramatic dual role of a component. After soaking the samplein ethanol, the filtration efficiency and fiber size was measured. Afteralcohol soak, 85.6% of filtration efficiency was retained and the fibersize was unchanged. This indicates that Polymer C has participated incrosslinking acting like a polymer solid.

Another polymer solution was prepared in the following manner:

Alkoxy alkyl Modified PA66: Polymer B 225 g Bisphenol A Resin (3,000MW): Polymer C 135 g Ethanol 190 Grade 778 g Acetone 205 g DI Water 157g Catalyst 11.6 g

Viscosity of this blend was 90.2 centipoise. This is a very lowviscosity value for 24% solid. Again, this is an indication Polymer Cacts like a solvent in the solution. However, when they are electrospuninto fiber, the fiber diameter is 0.438 micron. 15% solution of PolymerB alone would have produced around 0.2-micron fibers. In final state,Polymer C contributes to enlarging fiber sizes. Again, this exampleillustrates that this type of branched polymer acts as a solvent insolution and acts as a solid in final state. After soaking in ethanolsolution, 77.9% of filtration efficiency was retained and fiber size wasunchanged.

EXAMPLE 9 Development of Crosslinked Polyamides/Bisphenol A PolymerBlends

Three different samples were prepared by combining resins, alcohols andwater, stirring 2 hours at 60 degree C. The solution is cooled to roomtemperature and catalyst was added to solution and the mixture wasstirred another 15 minutes. Afterward, viscosity of solution wasmeasured and spun into fibers.

The following table shows these examples:

Recipe (g) Sample 9A Sample 9B Sample 9C Polymer B 8.4 12.6 14.7 PolymerA 3.6 5.4 6.3 Polymer C 7.2 10.8 12.6 Ethanol 190 Grade 89.3 82.7 79.5Isopropanol 23.5 21.8 21.0 DI Water 18.0 16.7 15.9 Catalyst .45 0.580.79 Viscosity (cP) 22.5 73.5 134.2 Fiber Size (micron) 0.14 0.258 0.496

We have found out that this blend generates fibers efficiently,producing about 50% more mass of fiber compared to Polymer A recipe. Inaddition, resultant polymeric microfibers produce a more chemicallyresistant fiber. After alcohol soak, a filter made from these fibersmaintained more than 90% filtration efficiency and unchanged fiberdiameter even though inherently crosslinkable polymer is only 44% of thesolid composition. This three-polymer composition of co-polyamide,alkoxy alkyl modified Nylon 66 and Bisphenol A creates excellent fiberforming, chemically resistant material.

EXAMPLE 10 Alkoxy Alkyl Modified Co-polymer of Nylon 66 and Nylon 46

In a 10-gallon high-pressure reactor, the following reactions were made,and resultant polymers were analyzed. After reaction temperature wasreached, catalyst were added and reacted for 15 minutes. Afterward, thepolymer solution was quenched, precipitated, washed and dried.

Reactor Charge Run Run Run Run Run (LB) 10A 10B 10C 10D 10E Nylon 4, 6(duPont 10 5 5 5 5 Zytel 101) Nylon 6, 6 (DSM 0 5 5 5 5 Stanyl 300)Formaldehyde 8 10 8 10 8 DI Water 0.2 0.2 2 0.2 2 Methanol 22 20 20 2020 Reaction Temp 140 140 140 150 150 (C. °) Tg (C. °) 56.7 38.8 37.738.5 31.8 Tm (C. °) 241.1 162.3 184.9 175.4 189.5 Level of Substi-tution Alkoxy (wt. %) 11.9 11.7 7.1 11.1 8.4 Methylol (wt %) 0.14 0.130.14 0.26 0.24

DSC of the polymer made with Nylon 46 and Nylon 66 shows broad singlemelt temperature, which are lower than the melting temperature ofmodified Nylon 46 (241° C.) or modified Nylon 66 (210° C.). This is anindication that during the reaction, both components are randomlydistributed along the polymer chain. Thus, we believe that we haveachieved random copolymer of Nylon 46 and Nylon 66 with alkoxy alkylmodification. These polymers are soluble in alcohols and mixtures ofalcohol and water.

Property ASTM Nylon 6.6 Nylon 4.6 T_(m) 265° C. 295° C. Tensile StrengthD638 13.700 8.500 Elongation at D638 15–80 60 Break Tensile Yield D638  8000–12,000 Strength Flexural Strength D790 17,8000 11,500 TensileModulus × D638 230–550 250 10³ psi Izod Impact ft- D256A 0.55–1.0  17lb/in of notch Deflection Temp D648 158 194 Under Flexural Load 264 psiBoth are highly crystalline and are not soluble in common alcohols.Source: Modem Plastics Encyclopedia 1998

EXAMPLE 11 Development of Interpolymer of Coplyamides and AlkoxyalkylModified Nylon 46/66 Copolymer and Formation of Electrospun Fibers

Runs 10B and 10D samples were made into fibers by methods described inabove. Alkoxy alkyl modified Nylon 46/66 (Polymer D) alone weresuccessfully electrospun. Blending Polymer D with Polymer A bringsadditional benefits of more efficient fiber formation and ability tomake bigger fibers without sacrificing the crosslinkability of Polymer Das can be seen in the following table:

Polymer 10B Polymer 10D w/30% w/30% Alone Polymer A Alone Polymer AFiber Size(micron) 0.183 0.464 0.19 0.3 Fiber Mass Ratio 1 3 1 2Filtration Effi. Retention(%) 87 90 92 90Fiber Mass Ratio is calculated by (total length of fiber times crosssectional area). Filtration Efficiency Retention is measured soakingfilter sample in ethanol. Fiber size was unchanged by alcohol soak.

EXAMPLE 12 Crosslinked, Electrospun PVA

PVA powders were purchased from Aldrich Chemicals. They were dissolvedeither in water or 50/50 mixture of methanol and water. They were mixedwith crosslinking agent and toluene sulfonic acid catalyst beforeelectrospinning. The resulting fiber mat was crosslinked in an oven at150° C. for 10 minutes before exposing to THC bench.

Sample 12A Sample 12B Sample 12C Sample 12D PVA Hydrolysis 98–99 87–8987–89 87–89 M.W. 31,500–50,000 31,500–50,000 31,500–50,000 31,500–50,000PVA 10 10 10 10 Conc. (%) Solvent Water Mixture Mixture (c) Mixture (d)Other Polymer None None Acrylic Acid Cymel 385 Other Polymer/ 0 0 30 30PVA (%) % Fiber 0 0 95 20 Retained THC, (a) (a, b) (b) (b) 1 hr. % Fiber90 Retained THC, (a) 3 hr. (a): Temperature 160° F., 100% humidity (b):Temperature 140° F., 100% humidity (c): Molecular Weight 2000 (d):Melamine formaldehyde resin from Cytec

EXAMPLE 13

A conventional cellulose air filter media was used as the substrate.This substrate had a basis weight of 67 pounds per 3000 square feet, aFrazier permeability of 16 feet per minute at 0.5 inches of waterpressure drop, a thickness of 0.012 inches, and a LEFS efficiency of41.6%. A fine fiber layer of Example 1 was added to the surface usingthe process described with a nominal fiber diameter of 0.2 microns. Theresulting composite had a LEFS efficiency of 63.7%. After exposure to140F air at 100% relative humidity for 1 hour the substrate only samplewas allowed to cool and dry, it then had a LEFS efficiency of 36.5%.After exposure to 140F air at 100% relative humidity for 1 hour thecomposite sample was allowed to cool and dry, it then had a LEFSefficiency of 39.7%. Using the mathematical formulas described, the finefiber layer efficiency retained after 1 hour of exposure was 13%, thenumber of effective fine fibers retained was 11%.

EXAMPLE 14

A conventional cellulose air filter media was used as the substrate.This substrate had a basis weight of 67 pounds per 3000 square feet, aFrazier permeability of 16 feet per minute at 0.5 inches of waterpressure drop, a thickness of 0.012 inches, and a LEFS efficiency of41.6%. A fine fiber layer of Example 5 was added to the surface usingthe process described with a nominal fiber diameter of 0.2 microns. Theresulting composite had a LEFS efficiency of 96.0%. After exposure to160F air at 100% relative humidity for 3 hours the substrate only samplewas allowed to cool and dry, it then had a LEFS efficiency of 35.3%.After exposure to 160F air at 100% relative humidity for 3 hours thecomposite sample was allowed to cool and dry, it then had a LEFSefficiency of 68.0%. Using the mathematical formulas described, the finefiber layer efficiency retained after 3 hours of exposure was 58%, thenumber of effective fine fibers retained was 29%.

EXAMPLE 15

A conventional cellulose air filter media was used as the substrate.This substrate had a basis weight of 67 pounds per 3000 square feet, aFrazier permeability of 16 feet per minute at 0.5 inches of waterpressure drop, a thickness of 0.012 inches, and a LEFS efficiency of41.6%. A fine fiber layer of a blend of Polymer A and Polymer B asdescribed in Example 6 was added to the surface using the processdescribed with a nominal fiber diameter of 0.2 microns. The resultingcomposite had a LEFS efficiency of 92.9%. After exposure to 160F air at100% relative humidity for 3 hours the substrate only sample was allowedto cool and dry, it then had a LEFS efficiency of 35.3%. After exposureto 160F air at 100% relative humidity for 3 hours the composite samplewas allowed to cool and dry, it then had a LEFS efficiency of 86.0%.Using the mathematical formulas described, the fine fiber layerefficiency retained after 3 hours of exposure was 96%, the number ofeffective fine fibers retained was 89%.

EXAMPLE 16

A conventional cellulose air filter media was used as the substrate.This substrate had a basis weight of 67 pounds per 3000 square feet, aFrazier permeability of 16 feet per minute at 0.5 inches of waterpressure drop, a thickness of 0.012 inches, and a LEFS efficiency of41.6%. A fine fiber layer of Polymer A, Polymer B, t-butyl phenololigomer as described in Example 6 was added to the surface using theprocess described with a nominal fiber diameter of 0.2 microns. Theresulting composite had a LEFS efficiency of 90.4%. After exposure to160F air at 100% relative humidity for 3 hours the substrate only samplewas allowed to cool and dry, it then had a LEFS efficiency of 35.3%.After exposure to 160F air at 100% relative humidity for 3 hours thecomposite sample was allowed to cool and dry, it then had a LEFSefficiency of 87.3%. Using the mathematical formulas described, the finefiber layer efficiency retained after 3 hours of exposure was 97%, thenumber of effective fine fibers retained was 92%.

EXAMPLE 17

A conventional cellulose air filter media was used as the substrate.This substrate had a basis weight of 67 pounds per 3000 square feet, aFrazier permeability of 16 feet per minute at 0.5 inches of waterpressure drop, a thickness of 0.012 inches, and a LEFS efficiency of41.6%. A fine fiber layer of crosslinked PVA with polyacrylic acid ofExample 12 was added to the surface using the process described with anominal fiber diameter of 0.2 microns. The resulting composite had aLEFS efficiency of 92.9%. After exposure to 160F air at 100% relativehumidity for 2 hours the substrate only sample was allowed to cool anddry, it then had a LEFS efficiency of 35.3%. After exposure to 160F airat 100% relative humidity for 2 hours the composite sample was allowedto cool and dry, it then had a LEFS efficiency of 83.1%. Using themathematical formulas described, the fine fiber layer efficiencyretained after 2 hours of exposure was 89%, the number of effective finefibers retained was 76%.

EXAMPLE 18

The following filter medias have been made with the methods described inExample 1–17.

Filter Media Examples Substrate Single fine fiber layer on Substratesingle substrate (flow perm Substrate Basis wt Substrate SubstrateComposite either direction through (Frazier) (lbs/3000 sq ft) Thickness(in) Eff (LEFS) Eff (LEFS media (+/− 10% (+/− 10%) (+/− 25%) (+/− 5%)(+/− 5%) Cellulose air filter media 58 67 0.012 11% 50% Cellulose airfilter media 16 67 0.012 43% 58% Cellulose air filter media 58 67 0.01211% 65% Cellulose air filter media 16 67 0.012 43% 70% Cellulose airfilter media 22 52 0.010 17% 70% Cellulose air filter media 16 67 0.01243% 72% Cellulose/synthetic blend 14 70 0.012 30% 70% with moistureresistant resin Flame retardant cellulose 17 77 0.012 31% 58% air filtermedia Flame retardant cellulose 17 77 0.012 31% 72% air filter mediaFlame retardant synthetic 27 83 0.012 77% air filter media SpunbondRemay 1200 15 0.007  5% 55% (polyester) Synthetic/cellulose air 260 760.015  6% 17% filter media Synthetic/glass air filter 31 70 0.012 55%77% media Synthetic/glass air filter 31 70 0.012 50% 90% media Singlefine fiber layer on substrate. Two layers of composite are thenlaminated together (fine fiber layers on the inside- substrates on theoutside) Synthetic (Lutrador- 300 25 0.008  3% 65% polyester) Synthetic(Lutrador- 0.016 90% polyester)

Media has been used flat, corrugated, pleated, corrugated and pleated,in flatsheets, pleated flat panels, pleated round filters, and Zeefilters.

Test Methods

Hot Water Soak Test

Using filtration efficiency as the measure of the number of fine fiberseffectively and functionally retained in structure has a number ofadvantages over other possible methods such as SEM evaluation.

-   -   the filtration measure evaluates several square inches of media        yielding a better average than the tiny area seen in SEM        photomicrographs (usually less than 0.0001 square inch    -   the filtration measurement quantifies the number of fibers        remaining functional in the structure. Those fibers that remain,        but are clumped together or otherwise existing in an altered        structure are only included by their measured effectiveness and        functionality.

Nevertheless, in fibrous structures where the filtration efficiency isnot easily measured, other methods can be used to measure the percent offiber remaining and evaluated against the 50% retention criteria.

Description: This test is an accelerated indicator of filter mediamoisture resistance. The test uses the LEFS test bench to measure filtermedia performance changes upon immersion in water. Water temperature isa critical parameter and is chosen based on the survivability history ofthe media under investigation, the desire to minimize the test time andthe ability of the test to discriminate between media types. Typicalwater temperatures re 70° F., 140° F. or 160° F.Procedure:A 4″ diameter sample is cut from the media. Particle capture efficiencyof the test specimen is calculated using 0.8 μm latex spheres as a testchallenge contaminant in the LEFS (for a description of the LEFS test,see ASTM Standard F1215-89) bench operating at 20 FPM. The sample isthen submerged in (typically 140° F.) distilled water for 5 minutes. Thesample is then placed on a drying rack and dried at room temperature(typically overnight). Once it is dry the sample is then retested forefficiency on the LEFS bench using the same conditions for the initialcalculation.The previous steps are repeated for the fine fiber supporting substratewithout fine fiber.From the above information one can calculate the efficiency componentdue only to the fine fiber and the resulting loss in efficiency due towater damage. Once the loss in efficiency due to the fine fiber isdetermined one can calculate the amount of efficiency retained.Calculations:

-   Fine fiber layer efficiency:    -   E_(i)=Initial Composite Efficiency;    -   E_(s)=Initial Substrate Efficiency;    -   F_(e)=Fine Fiber Layer        F _(e)=1-EXP(Ln(1−E _(i))−Ln(1−E _(x)))-   Fine fiber layer efficiency retained:    -   F_(i)=Initial fine fiber layer efficiency;    -   F_(x)=Post soak fine fiber layer efficiency;    -   F_(r)=Fine fiber retained        F _(r) =F _(x) /F _(i)        The percentage of the fine fibers retained with effective        functionality can also be calculated by:        %=log(1−F _(x))/log(1−F _(i))-   Pass/Fail Criteria: >50% efficiency retention    In most industrial pulse cleaning filter applications the filter    would perform adequately if at least 50% of the fine fiber    efficiency is retained.    THC Bench (Temperature, Humidity-   Description: The purpose of this bench is to evaluate fine fiber    media resistance to the affects of elevated temperature and high    humidity under dynamic flow conditions. The test is intended to    simulate extreme operating conditions of either an industrial    filtration application, gas turbine inlet application, or heavy duty    engine air intake environments. Samples are taken out, dried and    LEFS tested at intervals. This system is mostly used to simulate hot    humid conditions but can also be used to simulate hot/cold dry    situations.

Temperature −31 to 390° F. Humidity 0 to 100% RH (Max temp for 100% RHis 160° F. and max continuous duration at this condition is 16 hours)Flow Rate 1 to 35 FPM

-   Procedure:    A 4″ diameter sample is cut from the media.    Particle capture efficiency of the test specimen is calculated using    0.8 μm latex spheres as a test challenge contaminant in the LEFS    bench operating at 20 FPM.    The sample is then inserted into the THC media chuck.    Test times can be from minutes to days depending on testing    conditions.    The sample is then placed on a drying rack and dried at room    temperature (typically overnight). Once it is dry the sample is then    retested for efficiency on the LEFS bench using the same conditions    for the initial calculation.    The previous steps are repeated for the fine fiber supporting    substrate without fine fiber.    From the above information one can calculate the efficiency    component due only to the fine fiber and the resulting loss in    efficiency due to alcohol damage.    Once the loss in efficiency due to the fine fiber is determined one    can calculate the amount of efficiency retained.-   Pass/Fail Criteria: >50% efficiency retention    In most industrial pulse cleaning filter applications the filter    would perform adequately if at least 50% of the fine fiber    efficiency is retained.    Alcohol (Ethanol) Soak Test-   Description: The test uses the LEFS test bench to measure filter    media performance changes upon immersion in room temperature    ethanol.-   Procedure:    A 4″ diameter sample is cut from the media. Particle capture    efficiency of the test specimen is calculated using 0.8 μm latex    spheres as a test challenge contaminant in the LEFS bench operating    at 20 FPM. The sample is then submerged in alcohol for 1 minute.    The sample is then placed on a drying rack and dried at room    temperature (typically overnight). Once it is dry the sample is then    retested for efficiency on the LEFS bench using the same conditions    for the initial calculation. The previous steps are repeated for the    fine fiber supporting substrate without fine fiber. From the above    information one can calculate the efficiency component due only to    the fine fiber and the resulting loss in efficiency due to alcohol    damage. Once the loss in efficiency due to the fine fiber is    determined one can calculate the amount of efficiency retained.    Pass/Fail Criteria: >50% efficiency retention.

The above specification, examples and data provide an explanation of theinvention. However, many variations and embodiments can be made to thedisclosed invention. The invention is embodied in the claims hereinafter appended.

1. A filter element arrangement comprising: (a) a media pack having asubstrate comprising first and second opposite flow faces and aplurality of flutes wherein in said media pack; (i) each of said fluteshave a first end portion adjacent to said first flow face and a secondend portion adjacent to said second flow face; (ii) selected ones ofsaid flutes being open at said first end portion and closed at saidsecond end portion; and selected ones of said flutes being closed atsaid first end portion and open at said second end portion; (iii) saidsubstrate at least partially covered by a layer comprising fine fibercomprising a fiber with a diameter of about 0.01 to 0.5 microns, thefiber comprising a polymer and about 2 to 25% of resinous additive inthe form of a coating on the fiber such that the fiber, when testedunder conditions of exposure for a test period of 16 hours to testconditions of 140° F. air at a relative humidity of 100%, retainsgreater than 30% of the fiber unchanged for filtration purposes; and (b)a sealing system including a frame construction and a seal member; (i)said frame arrangement including an extension projecting axially fromone of said first and second flow faces, said extension comprises a hoopconstruction having an outer radial surface; (ii) said seal member beingsupported by said extension of said frame arrangement; (A) said sealmember comprising a resilient seal member; (B) said seal member beingoriented against at least said outer radial surface.
 2. The element ofclaim 1 wherein the polymer comprises an addition polymer.
 3. Theelement of claim 2 wherein the addition polymer comprises a polyvinylhalide polymer, a polyvinylidene halide polymer or mixtures thereof. 4.The element of claim 2 wherein the addition polymer comprises apolyvinylalcohol.
 5. The element of claim 2 wherein the addition polymercomprises a copolymer comprising vinylalcohol.
 6. The element of claim 4wherein the polyvinylalcohol is crosslinked with about 1 to 40 wt. % ofa crosslinking agent.
 7. The element of claim 5 wherein the polymer iscrosslinked with about 1 to 40 wt. % of a crosslinking agent.
 8. Theelement of claim 1 wherein the resinous additive comprises an oligomerhaving a molecular weight of about 500 to 3000 and an aromatic characterwherein the additive is miscible in the condensation polymer.
 9. Theelement of claim 1 comprising a condensation polymer.
 10. The element ofclaim 9 comprising a nylon polymer.
 11. The element of claim 10 whereinthe nylon comprises a nylon other than a copolymer formed from a cycliclactam and a C₆₋₁₀ diamine monomer or a C₆₋₁₀ diacid monomer.
 12. Theelement of claim 9 wherein the condensation polymer comprises apolyalkylene terephthalate.
 13. The element of claim 9 wherein thecondensation polymer comprises a nylon polymer comprising a homopolymerhaving repeating units derived from a cyclic lactam.
 14. The element ofclaim 10 wherein the nylon polymer is combined with a second nylonpolymer, the second nylon polymer differing in molecular weight ormonomer composition.
 15. The element of claim 11 wherein the secondnylon polymer comprises an alkoxy alkyl modified polyamide.
 16. Theelement of claim 14 wherein the second nylon polymer comprises a nyloncopolymer.
 17. The element of claim 14 wherein the polymers are treatedto form a single polymeric composition as measured by a differentialscanning calorimeter showing a single-phase material.
 18. The element ofclaim 17 wherein the copolymer and the second polymer are heat-treated.19. The element of claim 18 wherein the copolymer and the second polymerare heat-treated to a temperature less than the lower melting point ofthe polymers.
 20. The element of claim 18 wherein the additive comprisesan oligomer comprising a phenol compound.
 21. The element of claim 18wherein the additive comprises a blend of the resinous additive and afluoropolymer.
 22. The element of claim 18 wherein the fluoropolymercomprises a fluorocarbon surfactant.
 23. The element of claim 18 whereinthe additive comprises a nonionic surfactant.
 24. The element of claim 9wherein the condensation polymer comprises a polyurethane polymer. 25.The element of claim 9 wherein the condensation polymer comprises ablend of a polyurethane polymer and a polyamide polymer.
 26. The elementof claim 10 wherein the nylon comprises a nylon homopolymer, a nyloncopolymer or mixtures thereof.
 27. The element of claim 9 wherein thecondensation polymer comprises an aromatic polyamide.
 28. A filterelement arrangement according to claim 1 wherein said media pack andsaid frame construction have a circular cross-section.
 29. A filterelement arrangement according to claim 1 wherein said media pack andsaid frame construction have a racetrack shaped cross-section; and saidframe construction includes radially supporting cross braces.
 30. Afilter element arrangement according to claim 1 further including apanel structure; said media pack being mounted within said panelstructure.
 31. A filter element arrangement according to claim 1 furtherincluding a sleeve member secured to and circumscribing said media packsaid sleeve member being oriented relative said media pack to extend atleast 30% of said axial length of said media pack; and a seal memberpressure flange at least partially circumscribing said media pack saidseal member pressure flange extending radially from said sleeve memberand fully circumscribing said sleeve member.